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<DATE>2008-08-18</DATE>
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<NAME>John Pas</NAME>
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<DIV1 TYPE="title page">
<PB REF="1" MS="y">
<P><HI>DIFFICILES N&V;GAE:</HI> OR, OBSERVATIONS Touching the TORRICELLIAN <HI>Experiment,</HI> AND The various Solutions of the &s;ame, e&s;pecially touching the Weight and Ela&s;ticity of the AIR.</P>
<P><HI>LONDON,</HI> Printed by <HI>W. Godbid,</HI> for <HI>William Shrowsbury,</HI> at the Sign of the Bible in <HI>Duck-lane,</HI> M. DC.LXXIV.</P>
</DIV1>
<DIV1 TYPE="publisher to the reader">
<PB REF="2" MS="y">
<PB REF="2">
<HEAD>THE PUBLISHER TO THE READER.</HEAD>
<P>THE Title of this Book gives thee little incouragement to buy or to read it, and it was purpo&s;ely &s;o given. If it per|forms but as much as the Title pro|mi&s;eth, thou art not deceived; if more, thou art advantaged.</P>
<P>The Subject is &s;eemingly trivial, and &s;uitable to the Title; yet it hath exerci&s;ed the Wits and Pens of many Learned men, and makes way
<PB REF="3">to Natural Di&s;coveries, and con&s;e|quences of greater importance; at the wor&s;t it may be an innocent Diver|ti&s;ement, and po&s;&s;ibly delightful to tho&s;e that are plea&s;ed with Specula|tions and Experiments of this na|ture.</P>
<P>The Experiments therein are &s;ome new, &s;ome vulgar and common, and &s;ome borrowed from tho&s;e Excellent per&s;ons, whom though the Author highly honours for their Learning and Industry, yet in &s;ome things di&s;|&s;ents from them in their Solutions and Conclu&s;ions from tho&s;e Experi|ments that they have mo&s;t ingeni|ou&s;ly found out and delivered.</P>
<P>The Author pretends not to an equality of Learning to tho&s;e from whom he thus di&s;&s;ents, much le&s;s to Infallibility; there may po&s;&s;ibly hap|pen
<PB REF="3">want of Exactne&s;s in his Tryals, there may be imperfect and mi&s;taken Computations. The Diagrams though but few, yet rude. The Re&s;olutions and Conclu&s;ions may either be imper|fect, or not &s;o clearly or evidently ex|pre&s;&s;ed, and inferred, or deduced.</P>
<P>But he that con&s;iders the intri|cacy of this Inquiry, the various complications' of Cau&s;es, and Effects, and Appearances that occur therein, the great difficulty of arriving to exactne&s;s in the Experiments them|&s;elves, will rectify or ea&s;ily excu&s;e &s;uch mi&s;takes or inadvertencies, if any &s;uch occur in the&s;e Papers.</P>
<P>If the Inquiry hath not attained its full complement and perfection in the&s;e Papers, yet the Author hath obtained his End therein, namely, to give hints and occa&s;ions to Ingenious
<PB REF="4">per&s;ons to make farther and better Di&s;coveries, and to rectifie (if there be occa&s;ion) the mi&s;takes of the&s;e or other mens Solutions; and to give a little warning to men of Wit and Parts, not to be too ha&s;ty or po&s;itive in exterminating the <HI>Ari&s;totelian</HI> Philo&s;ophy, and entertaining new <HI>hypothe&s;es,</HI> 'till they have fully and maturely con&s;idered, and well looked about them. The Author's Name is not prefixed, for it would be of &s;mall advantage or u&s;e: and he is thereby the fitter to bear the correction of his Errors, and to retract them with more ea&s;e, and le&s;s ob&s;ervation, if a|ny &s;uch &s;hall occur to his di&s;covery or notice; and therefore hath left the Book it &s;elf, and the matters therein delivered, to bear their own burthen, and to &s;tand or fall as they de&s;erve.</P>
</DIV1>
</FRONT>
<BODY>
<DIV1 TYPE="text">
<PB N="1" REF="4">
<HEAD>Ob&s;ervations touching the <HI>Torri|cellian</HI> Experiment, and the Weight and Spring of Air.</HEAD>
<DIV2 N="1" TYPE="chapter">
<HEAD>CHAP. I.</HEAD>
<HEAD TYPE="sub"><HI>The Introduction, containing the order of the en&s;uing Enquiries.</HI></HEAD>
<P>_AMong the many Experi|ments of latter Ages, there hath been invented that Engine that commonly goes under the name of the <HI>Torricellian</HI> Experiment, which is but this: A Gla&s;s-Tube of three foot or more long, clo&s;ed at one end, and then filled with Mercury or Quick|&s;ilver, and then the open end &s;topped with the finger, and inverted into a ve&s;&s;el of re&s;tagnant Mercury &amp; and when the end is &s;ufficiently immer&s;ed, then the finger nimbly removed &s;o that
<PB N="2" REF="5">no Air get in, the Mercury will &s;ub&s;ide in the Tube to the height of <HI>29</HI> Inches, and half an inch, or near thereabout; but infallibly between 27 and 30 Inches, leaving the re&s;idue of the upper end of the Tube emptied of the Mercury.</P>
<P>This Experiment, and the &s;olution of it, hath exerci&s;ed the Tryals and Wits, and Invention of very many excellent Per&s;ons, &s;uch as were <HI>Helmont, Ga&s;&s;en|dus, Kircherus, Shottus,</HI> Dr. <HI>Carleton,</HI> Mr. <HI>Hobbs,</HI> Mr. <HI>Sinclere,</HI> Mon&s;ieur <HI>Pec|quett,</HI> Mon&s;ieur <HI>Pa&s;call, Magnanus,</HI> Mr. <HI>Boyle, Linus, Honeratus, Fabri,</HI> and divers others; who though men of great Learning and Indu&s;try, have run into &s;everal Parties, and given Soluti|ons, and rai&s;ed Conclu&s;ions from it, extreamly contradictory the one to the other.</P>
<P>And although this &s;eems but a very trifling and ludicrous Experiment, yet almo&s;t all di&s;&s;enting Parties have made it to &s;uffragate to their &s;everal precon|cerned Sentiments, and Per&s;wa&s;ions, and that in Philo&s;ophical Points of as great moment and importance per|chance
<PB N="3" REF="5">as mo&s;t to be found in na|tural Inquiries. Some from hence con|firm them&s;elves in their Per&s;wa&s;ion, that there are both inter&s;per&s;ed and coacervated Vacuities or Spaces, empty of any corporeal &s;ub&s;tance in the Uni|ver&s;e; others again as confidently con|cluding the untruth of that Opinion, and that from the &s;ame Experiment. Others again from hence confirming them&s;elves in the <HI>Carte&s;ian</HI> &s;uppo&s;iti|on of his <HI>Tria Principia,</HI> and e&s;pecially of that <HI>Materia Subtilis,</HI> which cannot be excluded from pervading the mo&s;t contumacious and &s;olid body: Others attributing the &s;ame Power to the more &s;ubtil parts of the aerial con&s;i&s;tence; &s;ome from hence concluding an actual pre&s;&s;ure and gravitation of the Air up|on all &s;ubjected bodies, and that there|by the Mercury is &s;u&s;teined by way of Pre&s;&s;ure, and Tru&s;ion, and Counterpoys, and have &s;ub&s;tituted thereupon as an undoubted <HI>Hypothe&s;is,</HI> a world of admi|rable con&s;equences in natural appea|rances, not only in the greater World, but al&s;o in the le&s;&s;er World the humane
<PB N="4" REF="6">&s;tructure. Others again have hereupon maintained their opinion of Attraction as the nece&s;&s;ary effect of Ten&s;ion, and re&s;olve this &s;u&s;pen&s;ion of the Mercury unto the force of attraction and &s;uction, occa&s;ioned by that Catholick Law of Nature for pre&s;ervation of the conti|nuity of the Univer&s;e, and all its parts, and the <HI>Fuga Vacui,</HI> and are no way &s;ati&s;|fied with that confidence that decryes it.</P>
<P>From this diver&s;ity of Judgments of Learned men, we may learn, fir&s;t, how little it is in natural Effects that we re|ally and truly know and under&s;tand, when &s;o trivial an Experiment that we have &s;o ea&s;ie an acce&s;s unto, and handle with our hands, and perceive by our &s;ight its motion, which yet &s;o gravels, or at lea&s;t divides men of great Parts, Judg|ment, Learning and Experience. 2. How &s;trangely partial men are to tho&s;e Sentiments that they have once enter|tained, and perchance taken much pains to mould and fa&s;hion, or have even publickly engaged unto or for; whereby it comes to pa&s;s that men are not wil|ling
<PB N="5" REF="6">impartially to con&s;ider what makes again&s;t their opinion, and frame a thou&s;and imaginations to evade the &s;trength of the oppo&s;ite rea&s;ons, and to con&s;true all appearances (as melan|cholick per&s;ons do the &s;ound of Bells) to &s;peak what they fancy; And po&s;&s;i|bly all the oppo&s;ite Opinators in this bu&s;ine&s;s are under the like partiality and unindifferency.</P>
<P>There is a great odds between a Mat|ter propounded only as an Hypothe&s;is, and propounded as a real truth. In the former there is nothing more required than a true under&s;tanding of the <HI>Phae|nomena,</HI> and a ready Wit to contrive &s;ome Model, and to dre&s;s it up &s;o hand|&s;omly, that it may an&s;wer the <HI>Phaeno|mena,</HI> and to fit up &s;uch expedients as may meet with and &s;top the Leaks that otherwi&s;e would happen in the Hypo|the&s;is: And &s;uch a man tells us not &s;o much what the truth of Nature is, as what he thinks he could have made it, if he had had the handling of it; &s;uch may be the Sy&s;temes of <HI>Ptolomy, Copernicus,</HI> and <HI>Tycho Brahe,</HI>
<PB N="6" REF="7">which cannot be po&s;&s;ibly all true, though po&s;&s;ibly they may be all fal&s;e. And yet every of them is &s;o fitted and accommodated by the Wit, Invention, and Indu&s;try of the Authors, that they &s;olve the <HI>Phaenomena</HI> very near equally: And thus if I remember aright <HI>des Cartes</HI> fairly propounds his <HI>tria Principia</HI>'s; and &s;ome other parts of his New Philo&s;o|phy.</P>
<P>But to propound a thing as really a truth in Nature, is another kind of bu|&s;ine&s;s, and requires not &s;o much a dex|trous Invention, but an impartial in|&s;pection into the things them&s;elves, and examination how all things &s;tand one with another, as we truely find them, and not as we mind to make them: For the Laws of Nature are &s;table, and &s;etled, and regular, and not like the Laws of Men, or the fa&s;hions of our Cloaths, mutable, according to new Modes, or devices of Fancy.</P>
<P>Therefore the bare accommodation of Hypothe&s;es to the Solution of the mo&s;t obvious <HI>Phaenomena</HI> is not always the mea&s;ure of its truth, for that may
<PB N="7" REF="7">be but the product of Invention and Wit. For it is apparent, that though it is impo&s;&s;ible that all the varying So|lutions of this trifling Experiment can be all true, yet they are all &s;o dre&s;&s;ed and pieced up, that they do &s;olve the mo&s;t obvious <HI>Phaenomena</HI> in this Experiment, well near equally each with other.</P>
<P>But on the other &s;ide, if any <HI>Phaeno|mena</HI> happen cleerly either in this or any other in&s;tance, that do cro&s;s and thwart that which is taken up as a nece&s;&s;ary <HI>po&s;tulatum</HI> in any of the&s;e Solutions; it is if not an undeniable, yet a great and po&s;&s;ibly a clear demon&s;tration, that the Hypothe&s;is its &s;elf is fal&s;e, and ill Founded, e&s;pecially if it be the great <HI>Ba&s;is</HI> upon which &s;uch Hypothe&s;is is bottomed and built.</P>
<P>And if the foundation of a Hypothe|&s;is, or the general <HI>po&s;tulatum</HI> upon which it is bottomed, be fal&s;e, or only imagi|nary, although the Inferences and Con|clu&s;ions made upon &s;uch a <HI>Ba&s;is</HI> be de|duced with all the finene&s;s and &s;ubtilty imaginable, and &s;uch (as were the <HI>po&s;tula|tum</HI> it &s;elf true, upon which they are bot|tomed)
<PB N="8" REF="8">would be as nece&s;&s;ary and con&s;equential, as the Demon&s;trati|ons of <HI>Euclide,</HI> yet the whole fabrique will fail when it comes to tryal, and be|come like the A&s;trological Predictions Calculated with Art enough upon a fal&s;e Ephemerides.</P>
<P>I that come after the Labours and Scrutinies of &s;o many Excellent Men that have gone before me upon this Subject, cannot promi&s;e my &s;elf or others that I &s;hall &s;ay much in this Matter that hath not been &s;aid before; and the ne|ce&s;&s;ity of a free Di&s;cour&s;e requires that I &s;hould take in &s;omewhat of other mens Labours. But I &s;hall avoid, as much as I can, the imputation of a Plagiary, by mentioning the Authors as I have oc|ca&s;ion: But yet, though &s;omewhat that I &s;hall &s;ay hath been &s;aid before, e&s;peci|ally by <HI>Linus,</HI> and <HI>Fabri,</HI> yet &s;omewhat will be new, although the mo&s;t I &s;hall do herein will be to make the Me|thod and manner of Explication of it as much my own as I can, which I &s;hall do in this order.</P>
<P>Fir&s;t, I &s;hall explain &s;ome Termes
<PB N="9" REF="8">which I &s;hall have occa&s;ion to u&s;e, that &s;o I may write intelligibly according to that &s;en&s;e I gave my words; though it may be po&s;&s;ibly not according to the &s;en&s;e wherein others have u&s;ed them.</P>
<P>Secondly, as preliminary to what I &s;hall &s;ay touching this Experiment, I &s;hall &s;et down &s;ome Statical Ob&s;ervati|ons, that may be u&s;eful to me upon this inquiry, not that I &s;hall ingage my &s;elf in the whole Theory of Statical Principles and conclu&s;ions; this hath been done already by tho&s;e worthy Per|&s;ons that have <HI>ex profe&s;&s;o</HI> handled this Subject, as <HI>Archimedes, Steving,</HI> Mr. <HI>Boyl,</HI> and others; but only &s;hall glean up &s;ome general Ob&s;ervations therein ne|ce&s;&s;ary to this inquiry.</P>
<P>Thirdly, I &s;hall &s;et down what it is not, that may be &s;uppo&s;ed in the &s;pace derelicted by the Mercury, namely, it is not Nothing, nor Ayre, nor <HI>Aether,</HI> nor any Body that comes from without.</P>
<P>Fourthly, I &s;hall &s;et down what I think it is that po&s;&s;e&s;&s;eth the place de|relict by the Mercury.</P>
<P>Fifthly, I &s;hall &s;et down what I think
<PB N="10" REF="9">is not the cau&s;e that &s;u&s;pends the Cylin|der of Mercury, in the Tube to that Altitude of 29 Inches, or thereabouts; namely, not the Gravitation or pre&s;&s;ure of the impending Ayr, nor its Ela|&s;tricity.</P>
<P>Sixth, I &s;hall &s;et down what I think is the cau&s;e, that &s;u&s;pends the column of Mercury from &s;ub&s;iding in the Tube be|low Twenty nine Inches, or thereabouts.</P>
<P>Seventhly, I &s;hall &s;et down tho&s;e ob|jections, that &s;eem of the greate&s;t force again&s;t the la&s;t &s;uppo&s;ition.</P>
<P>Eighthly, I &s;hall take a particular ex|amination of &s;ome other Experiments, as touching the cohe&s;ion of Poli&s;hed Marbles, and the <HI>Magdeburgh</HI> Hemi|&s;phere, and the ri&s;ing of Water in the common Pumps.</P>
<P>And this Order I &s;hall as near as I can ob&s;erve in the en&s;uing Chapters.</P>
</DIV2>
<DIV2 N="2" TYPE="chapter">
<PB N="11" REF="9">
<HEAD>CHAP. II.</HEAD>
<HEAD TYPE="sub"><HI>The Explication of &s;ome Terms, that may be of u&s;e in the following Inquiry.</HI></HEAD>
<P N="1">FIr&s;t, I &s;hall ob&s;erve the difference between the &s;pecifical or intrin|&s;ique Weight of a heavy Body, and the extrin&s;ique Weight or <HI>pondus molis.</HI></P>
<P>For in&s;tance, a pound of Mercury, and a hundred pound of Mercury, have the &s;ame intrin&s;ique Weight, but yet not the &s;ame extrin&s;ique Weight: A pound of Water and a pound of Mer|cury have the &s;ame extrin&s;ique Weight, for each quantity weighs but a pound, but they have not the &s;ame intrin&s;ique Weight, for quantity for quantity, Mer|cury is heavier then Water.</P>
<P>Tho&s;e Bodies are &s;aid to have the &s;ame &s;pecifical or intrin&s;ique Weight, when the &s;ame bulk or quantity coun|terpoi&s;eth equally the other; and tho&s;e Bodies are &s;aid to differ in intrin&s;ique Weight, where a greater quantity of the one is required to Equiponderate a
<PB N="12" REF="10">le&s;s quantity of the other; as for in|&s;tance, a Cylinder of Mercury, of an Inch long, and half an Inch Diameter, counterpoi&s;eth a Cylinder of Water of the &s;ame Diameter and 13 Inches &frac12; or 14 Inches long, or thereabouts. But although a Body &s;pecifically or intrin|&s;ically lighter than another, may in &s;ome ca&s;es have the advantage in point of &s;peed in motion of a Body of equal extrin&s;ical Weight, becau&s;e it takes up le&s;s room, and &s;o meets with le&s;s re&s;i|&s;tance in the <HI>medium,</HI> yet upon the Scale they equally counterpoi&s;e each other.</P>
<P>But again, there is this difference be|tween them; a Body of a greater intrin|&s;ique or &s;pecifical Gravity of an equal ex|trin&s;ique Weight, with a Body of le&s;s in|trin&s;ique weight, will &s;ometimes equally pre&s;s upon a Fluid Body, upon its Super|ficies, but will pre&s;s more than the ligh|ter, when both have the advantage to get below the Superficies; for in&s;tance,</P>
<P>Take a pound of Lead, and a pound of Wood, whether lighter or heavier than a quantity of Water equal to it,
<PB N="13" REF="10">lay them each upon a peece of Cork that will &s;upport them in the Water; the pound of Lead, and the pound of Cork will both &s;wim upon the Water.</P>
<P>But if the Cork be taken away, the Led will &s;ink, and the Wood will &s;wim if lighter than a like quantity of Wa|ter, and if heavier than the like quan|tity it will &s;ink, but not &s;o fa&s;t as the Led.</P>
<P N="2">2. There is a difference between an intrin&s;ique Weight, and an accidental Weight, which may be various; as for in&s;tance:</P>
<P>In re&s;pect of the po&s;ition of the one and the other: Water and Water are both intrin&s;ically of the &s;ame Weight, yet if Water be in a Tube, open at both ends, and be &s;topt with the Finger at the lower end, and then when contiguous to the Water in a Ve&s;&s;el, the lower end it is opened, all the Water in the Tube will &s;ub&s;ide to an equal Superficies with the Water in the Ve&s;&s;el, becau&s;e its higher po&s;ition gives it an accidental Weight more than that in the Ve&s;&s;el.</P>
<P>So again, Ayr and Ayr have the &s;ame
<PB N="14" REF="11">Weight, though it be hardly mea&s;urable, but if Ayr be compre&s;&s;ed as in a Wind|gun, it gains an accidental Gravity by its Compre&s;&s;ion of parts more than the common Ayr.</P>
<P N="3">3. There is a difference in Terms between Gravitation, and pre&s;&s;ure of heavy Bodies; for in&s;tance, A Tube &s;topt at the upper end, and driven down in a Ve&s;&s;el of Water forcibly, the pre&s;|&s;ure of the Water upon the Ayr in the Tube, will contract the Ayr as much as it can (&s;uppo&s;e it an Inch) and the re&s;t of the Ayr in the Tube will pre&s;s upon the Water, becau&s;e it will not yield more to the Water; this is pro|perly Pre&s;&s;ure in the Ayr upon the Wa|ter, and of the Water upwards upon the Ayr; yet neither are properly Gra|vitation, though po&s;&s;ibly, I may in &s;ome pa&s;&s;ages u&s;e the words promi&s;cuou&s;ly.</P>
<P N="4">4. There is a difference between Gravitation <HI>ad motum,</HI> which I call &s;ometime &s;en&s;ible or perceptible Gra|vitation, and Gravitation <HI>ad pondus,</HI> which I &s;ometimes call real or in&s;en&s;ible, or Phy&s;ical Gravitation: For in&s;tance,</P>
<PB N="15" REF="11">
<P>If a cubical Ve&s;&s;el of Water contain 56 pound weight of Water, and a piece of Cork, or parcel of Oyl of two pound weight be placed upon the top of the Water, it will not &s;en&s;ibly gravitate, but will be born up by the upper Su|perficies of the Water, whereunto the lower Superficies of the Cork or Oyl will be contiguous, becau&s;e being &s;pe|cifically or intrin&s;ecally lighter than Water, it is &s;u&s;tained by it, and makes no motion in the &s;ubjected Water.</P>
<P>(<HI>Fig.</HI> I.) But yet it is plain that in concretion with the water, the whole weighs 58 pound, whereas before the water alone weighed but 56 pound; &s;o that here is a gravitation <HI>ad pondus</HI> ad|ded hereunto <HI>in concreto</HI> to the water. But let us &s;uppo&s;e that the Ve&s;&s;el <HI>A, B, C, D,</HI> be filled with water unto the &s;u|perficies <HI>C, D,</HI> and the tube <HI>E,</HI> open at both ends be immer&s;ed into the water, and then a quantity of oyl, that is lighter &s;pecifically than water, be poured upon the &s;uperficies of the water; this will rai&s;e the water into the tube <HI>E,</HI> above the common &s;uperficies of the water, to
<PB N="16" REF="12">&s;uch a proportion of height in the Tube as will countervail the weight of a like Cylinder of Oyl, which will be &s;ome. what near to the &s;uperficies of the Oyl, becau&s;e the water at <HI>G,</HI> is not equally pre&s;&s;ed with the re&s;t of the &s;uperficies of the water by the incumbent Oyl. The di&s;parity of the pre&s;&s;ure cau&s;ing motion or elevation of the water in the part not equally pre&s;&s;ed; &s;o it is <HI>gra|vitatio ad motum,</HI> and not &s;imply <HI>ad pon|dus.</HI> So if upon a ve&s;&s;el of water there be placed a Body &s;pecifically heavier than water, but not exactly commen|&s;urate to its &s;uperficies; here is <HI>gravi|tatio ad motum,</HI> as well as <HI>ad pondus;</HI> for the body &s;inking into the water mu&s;t needs rai&s;e up as much water as the &s;pace it &s;elf takes in &s;ub&s;iding into the ve&s;&s;el of water.</P>
<P>And upon the &s;ame account it is, if the &s;ub&s;iding body be a Fluid, as <HI>Mer|cury,</HI> it will by &s;inking into the water drive up as much water as the room it takes, and &s;o make the &s;uperficies high|er; &s;o that an unequal pre&s;&s;ure of any Fluid mu&s;t nece&s;&s;arily make a motion
<PB N="17" REF="12">upwards of the parts of it, and thereby rai&s;e the &s;uperficies by &s;o much in bulk of water as will countervail the room that the immer&s;ed body takes up in the water. And this and the like I call &s;en&s;ible gravitation, or gravitation <HI>ad motum.</HI></P>
<P N="5">5. There is a difference between <HI>Pon|dus,</HI> and <HI>Potentia;</HI> and this is well enough evidenced in the in&s;tance of the Oyl and Water above given: The oyl gra|vitates upon all the &s;uperficies of the water, except that &s;ubjected to the ori|fice of the Tube <HI>E</HI> there is the <HI>pondus</HI> of the oyl and the water driving up, and &s;u&s;taining the water in the Tube to that height that equiponderates a like column of oyl there is the <HI>Potentia.</HI></P>
<P>Mr. <HI>Sinclere</HI> and others, that contend for the Solution of the <HI>Torricellian</HI> Ex|periment by the Gravitation of the Ayr, apply this difference unto two in|&s;tances, which po&s;&s;ibly in the event of their Examination will appear otherwi&s;e; namely: 1. That the Ayr equally pre&s;&s;ing the re&s;tagnated Mer|cury in all places thereof, but that
<PB N="18" REF="13">which is directly under the column of the &s;u&s;pended Mercury, and thereby Equiponderating a column of Mercury only of <HI>29</HI> Inches &frac12; and no more, keeps it &s;u&s;pended at that height by the Equi|pondium of both, there is the Gravita|tion of the column of Mercury, which is the <HI>pondus,</HI> and the Impending column of Ayr, which is the <HI>potentia &s;u&s;tinens,</HI> that Counterpoy&s;eth that <HI>pondus.</HI> I &s;hall have occa&s;ion to u&s;e this difference of <HI>pondus</HI> and <HI>potentia,</HI> in relation to this Experiment al&s;o, but in a different way. 2. The other in&s;tance, to which he ap|plies this difference, is in all Fluids, whether Ayr, Water, Mercury, or any el&s;e: Namely, if a Body be in any depth of Water; &s;uppo&s;e above it were 20 foot of Water, and below it two, three, or four Foot of Water, or more, &s;ubjacent to the lower Ba&s;e of the Body. The upper column of Water is &s;uppo|&s;ed to pre&s;s downwards, <HI>per modum pon|deris,</HI> upon the upper Superficies of the Body, and the lower column of Water, contiguous to the lower Superficies of the Body, is &s;uppo&s;ed to pre&s;s upwards,
<PB N="19" REF="13"><HI>per modum potentioe.</HI> And he &s;uppo&s;eth that the pre&s;&s;ure of the <HI>potentia</HI> up|wards, is alwayes equal to the pre&s;&s;ing of the <HI>pondus</HI> downward: This is a &s;up|po&s;ition fitted principally for the ac|commodating of the Solution of the Cohe&s;ion of Poli&s;hed Marbles, by the Gravitation and <HI>potentia</HI> of the Ayr, pre&s;&s;ing upwards and downwards, and &s;ome other in&s;tances, whereunto the &s;ingle Gravitation of Ayr down|wards will not be &s;ufficient: The proof whereof will be con&s;idered hereafter.</P>
<P N="6">6. There is a difference between the re&s;i&s;tence or Renitence of a Fluid, and the Gravitation or pre&s;&s;ure thereof: If a man &s;trikes forcibly with the flat of his hand upon the Superficies of the Water, he &s;hall find near as much pain as if he &s;truck upon a Board, although the Water doth not counter-move the hand, but receives and re&s;i&s;ts its &s;udden force; the like occurs frequently in Ayr: The fierce &s;triking of a wand through it, bends the wand, and the fierce Colli&s;ian of the Bullet again&s;t it, is not without a re&s;i&s;tence of the Ayr,
<PB N="20" REF="14">though too weak to encounter it.</P>
<P>And this Renitence or re&s;i&s;tence, without any counter-motion at all by the Water, is that which makes the Motion of the &s;ame heavy Body through the Water con&s;iderably &s;lower than through the Ayr; and the &s;ame Weight of Led or Iron, or other heavy Body in Water, to weigh le&s;s upon the Scale, than when it is in Ayr, the re|tardation of its Motion, and the cor|rection of its weight, being the &s;ame effect of the &s;ame Cau&s;e; namely, the re&s;i&s;tence of the Water, greater than in the Ayr, without relation to any counter-motion, or counter-pre&s;&s;ure in the Water it &s;elf.</P>
<P N="7">7. There is a difference between Rarefaction and Tention, and between Conden&s;ation and Compre&s;&s;ion, though the effects be much alike in both.</P>
<P>Rarefaction, (for in&s;tance, of the Ayr) is the Extention of its parts, commonly by heat, or what is equivo|lent, the fiery Partacles that it receives, whether from the Sun, the <HI>Aether,</HI> or common fire, or other Calefactive nature.</P>
<PB N="21" REF="14">
<P>Ten&s;ion, is when the parts of the Ayr are di&s;tended by virtue of &s;ome force or power that layes hold of its Ex|tremes, as a Lute-&s;tring is under a Ten|&s;ion to a greater length, by a con&s;idera|ble weight appended to it; only it hath this difference, a Lute-&s;tring or the like, is not capable of Ten&s;ion in length, but it mu&s;t have a contraction in thickne&s;s, but Ayr as it hath a motion every way, &s;o it is capable of Ten&s;ion every way.</P>
<P>The effects a&s;wel of Ten&s;ion as Rare|faction, are the&s;e, <HI>viz.</HI> the &s;ame &s;ub|&s;tance holds thereby a greater and more extended &s;pace. 2. The Body, thus either by heat or force, Rarefied or Ten&s;ed beyond its true natural &s;ize and &s;taple, hath a Motion of re&s;titution, na|rurally contracting it &s;elfd, and pre&s;&s;ing inward. 3. The Body thus contra|cting it &s;elf, by the Catholick Law of Nature, to pre&s;erve the continuity of the World, layes hold upon the Bodies next adjacent, and conterminous to it, and as much as it can draws it inward.</P>
<P>Again, Conden&s;ation and Compre&s;|&s;ion differ in this, that the former is
<PB N="22" REF="15">commonly made by the Con&s;tipation of Cold; the latter, by any other for|cible pre&s;&s;ure, as in Wind-guns, Aeoli|piles, and the like.</P>
<P>They both agree in their effects. 1. That the Ayr Conden&s;ed or Com|pre&s;&s;ed, takes up le&s;s room or &s;pace, than its natural and due &s;ize. 2. That they have each a Motion of re&s;titution, by ex|panding it &s;elf to its ju&s;t &s;ize.</P>
<P>And this Elatory or Spring, I allow to the Ayr; namely, of retraction, and expan&s;ion, when put out of its natural &s;ize or &s;taple: But the imaginary pro|digious Spring, attributed to the com|mon Ayr, as its natural tendency, I take to be only invention.</P>
<P>It is hard to &s;ay to what proportion Ayr may be Rarefied or Ten&s;ed; &s;ome think to above 70 times its common ex|ten&s;ion, or to what degree it may be Conden&s;ed or Rarefied; &s;ome think to &s;even, nine, or ten times, le&s;s then its ordinary con&s;i&s;tences, or more: <HI>Quod vide apud</HI> Mor&s;en <HI>in pneumaticis, et aliis.</HI></P>
<P N="8">8. There is a difference between the common Gravitation of a Fluid of
<PB N="23" REF="15">any kind, as it is a heavy Body, and the appropriate Gravitation of it as it is a Fluid Body: In re&s;pect of the former, it doth as all heavy Bodies, pre&s;s per|pendicularly downward towards the Centre; But as it is a Fluid Body, it hath an appropriate Gravitation of its own, whereby it corrects and allayes in &s;ome &s;ort, its common Gravitation: For in&s;tance, Water in its own con&s;i|&s;tency, hath a lateral Motion, a Motion <HI>per decliv&egrave;,</HI> an Hori&s;ontal Motion, within the compa&s;s of its own Super|ficies; yea, and a Vertical Motion up|ward, within the compa&s;s of its own Superficies: As if a Tube full of Ayr, &s;topt below, be immer&s;ed into Water, and then un&s;topped, the Water will heave as freely upward as it would otherwi&s;e downward, till it attain its own common level or Superficies; and &s;utable to its Motion is its Gravitation, which is nothing el&s;e but <HI>motus,</HI> or <HI>cona|tus ad motum.</HI></P>
<P>And be&s;ides this appropriate Gravi|tation of Fluids, there is a certain pro|per and connatural Texture in Fluids,
<PB N="24" REF="16">and e&s;pecially in Ayr, whereby the &s;ub|jected parts do &s;u&s;pend, and hold up con&s;iderably the Superior parts from any con&s;iderable Gravitation, &s;o that no Body, or portion of &s;pace le&s;s than the whole Ba&s;e of the whole Fluid is con&s;iderably pre&s;&s;ed upon by any &s;uch imaginary Column Commen&s;urated to the Ba&s;e of the &s;ubjected Fluid, as hath been el&s;ewhere ob&s;erved, and will be further Illu&s;trated in &s;ome of the following Chapters.</P>
<P N="9">9. There is a common and allowable difference beween the pure Ayr, &s;uch as may be in the upper Region, and that which is now commonly called the Atmo&s;phere. The former is &s;o pure and &s;ubtil, that the greate&s;t pre|tenders to the Ayrs Gravitation that I have &s;een, do not take upon them to to determin, that it hath any Weight.</P>
<P>The Atmo&s;phere, is that portion of the Ayr that is the common receptacle of Vapours, and the <HI>Effluvia</HI> of the Earth and Water, whereby it is le&s;s &s;ubtil than the pure Ayr.</P>
<P>Though &s;ome, out of the confidence
<PB N="25" REF="16">they have of their attaining the ju&s;t pro|portion of weight between Water and Ayr, and the ju&s;t proportion of weight between Mercury and Water, and upon the high confidence they have of the ju&s;t <HI>Equipondium</HI> between 29 Inches &frac12; of Mercury, and a Column of Atmo&s;phere of the &s;ame thickne&s;s with the Column of Mercury, have undertaken, to define the ju&s;t height of the Atmo&s;phere; &s;ome determining it to be ju&s;t 7000 Fathoms, &s;ome 7 Miles; yet the Doctors much differ among them&s;elves in their ac|count; &s;ome telling us, they take it to be 22 Miles high, others 50, others above 100.</P>
<P>And there mu&s;t needs be an excee|ding incertainty in this way of Com|puting it. For fir&s;t, Though the ju&s;t proportion of weight between the Quick&s;ilver and Water is ea&s;ily and cer|tainly di&s;covered to be truly as <HI>Mer&s;en|nus,</HI> and others, have accounted it, <HI>viz.</HI> that one Cubick Inch of Mercury will ju&s;t counterpoi&s;e 13 Cubick Inches and &frac12; of Water; yet the proportion of weight that Ayr bears to Water, (if it
<PB N="26" REF="17">have any real weight at all,) is not to be exactly Calculated, what&s;oever Expe|riments have been made thereof by <HI>Mer&s;ennus</HI> and others; the former tel|ling us, that the weight of Water to Ayr, is as one to about 1300; the others telling us it is as one to 1000, or at lea&s;t &s;ome &s;mall proportion le&s;s. 2. Admit the proportion were ju&s;tly known, yet tho&s;e that take their mea|&s;ure of the height of the Atmo&s;phere, or Gravitating Ayr, (if any &s;uch be) by the &s;uppo&s;ed <HI>Equipondium,</HI> between 29 Inches &frac12; of the &s;u&s;pended Mercury; and a Column of Ayr commen&s;urate in thickne&s;s to &s;uch a Mercurial Co|lumn, have bottomed them&s;elves, as I think, upon a fal&s;e Foundation. 3. But if it were true, as they would have it, yet even upon their own principles, it is extremely mi&s;taken and convinced by their own &s;uppo&s;itions and Experi|ments, as &s;hall be ob&s;erved in the en&s;u|ing Chapters.</P>
<P>And thus far to render my &s;elf intelli|gible in my expre&s;&s;ions in the future Inquiry.</P>
<PB N="27" REF="17">
<P>I &s;hall only add &s;ome Matters that will be u&s;eful as to the point of Calcu|lation.</P>
<P>The weight of Water is various, according to &s;everal places; <HI>Stevin</HI> tells us, that in &s;ome parts of <HI>Holland,</HI> a Cubique Foot of Water weighs <HI>63</HI> pound; as I remember, Mr. <HI>Sinclere</HI> Computes it to <HI>56</HI> pound, and con&s;e|&s;equently, a Cube of Water <HI>6</HI> Inches &s;quare, weighs 7 pounds; and I have by tryal found, that it weighs 7 pounds wanting two Ounces; but the Stan|dard of <HI>56</HI> pound and 7 pound, ordina|rily &s;utes the proportion of weight of tho&s;e two Bodies: Upon tryal, I have found the proportion very little diffe|ring, <HI>viz.</HI> a Cube of <HI>6</HI> Inches &s;quare of Water to weigh 7 pound wanting two Ounces, and con&s;equently a Cu|bical Foot to weigh 55 pound 4 Ounces.</P>
<P>The readie&s;t way to avoid Fractions and the long proce&s;s of Arithmetical Calculations, is by immer&s;ing any re|gular or other Solid Body into a Ve&s;&s;el full of Water, and to &s;ave that which
<PB N="28" REF="18">is impelled over by the immer&s;ion of the Solid Body, to di&s;cover the proportion of weight between &s;uch a Solid, and a Fluid of the &s;ame Moles or Dimen&s;i|ons.</P>
<P>The mea&s;ure of a Cubique or Square Body, is by Multiplying the one &s;ide into the other, to find the Area of In|ches; and by Multiplying the Area by the mea&s;ure of Inches in profundity.</P>
<P>The mea&s;ure of a Cylinder is by multiplying half the Diameter into half the Circumference, which yields the Area, and Multiplying the Area (of Inches) into the number of Inches, in the depth of the Cylinder: I mention the&s;e Figures, becau&s;e the mo&s;t ordina|ry and u&s;eful in Hydro&s;tatiques.</P>
<P>Mercury is thirteen times and an half and &s;omewhat more heavier than the like quantity of Water, as I have found upon tryal: If it be taken four|teen times heavier, it will not be much out of the way, and avoids Fractions. And therefore upon that computation, if a Cube of &s;ix Inches Square of Water weighs &s;even pound, a like
<PB N="29" REF="18">Cube of Mercury will weigh 98 pound Averdupoi&s;e.</P>
<P>The often u&s;e of Mercury even in the <HI>Torricellian</HI> Experiment, but e&s;pe|cially, where there is occa&s;ion of fre|quent Superfu&s;ion or Infu&s;ion of Wa|ter in the operation, will certainly much alter its Texture, Weight, and U&s;e, as I have Experimentally found.</P>
<P>It is a matter of great difficulty to avoid the immi&s;&s;ion of Ayr in the <HI>Torricellian</HI> Experiment, which will much di&s;order the operations.</P>
</DIV2>
<DIV2 N="3" TYPE="chapter">
<PB N="30" REF="19">
<HEAD>CHAP. III.</HEAD>
<HEAD TYPE="sub"><HI>Concerning the Gravitation of Bodyes; and fir&s;t, concerning the Gravitation of Fluids, in relation to Fluids of the &s;ame kind and con&s;i&s;tence: And therein al&s;o, fir&s;t of the Gravitation of Water upon water.</HI></HEAD>
<P>ALL heavy Bodyes have a Phy&s;ical Gravitation belonging to them, as the natural effect of that Gravity; for Gravitation is either Motion, or <HI>conatus ad motum,</HI> which is the natural effect or action of Gravity.</P>
<P>And yet although the parts of all continued Homogeneal heavy Bodies participate of the &s;ame common Gra|vity, that is common to the whole <HI>continuum;</HI> Tho&s;e parts are impeded in their actual or &s;en&s;ible Gravitation one upon another, by the &s;upport that each inferiour part gives to the &s;uperi|our parts, as the upper parts of a Cube of Lead do not actually Gravitate upon
<PB N="31" REF="19">the inferior parts, becau&s;e the upper are Mechanically impeded by the lower, from their actual Gravitation upon them; yet every Atom thereof con|tributes to the Gravitation of the whole upon the Scale.</P>
<P>But if the Solid Body be not all of the &s;ame con&s;i&s;tence, but the lower are of a lighter or more laxe Texture, or con&s;i&s;tence than the upper, there the upper parts will not only Phy&s;ically and really, but Mechanically and &s;en&s;ibly Gravitate upon the lower, according to the mea&s;ure of their exce&s;s of weight and &s;olidity above the lower, as if the upper part of a concrete Cube con&s;i&s;ts of Lead, and the lower parts of Clay, in proce&s;s of time, at le&s;t the upper will crumble away and decay the lower, by their more prevalent Gravitation, and the impority of the re&s;i&s;tence and &s;u&s;tentation of the lower.</P>
<P>Touching the Gravitation of Fluids upon Fluids, of the &s;ame kind and con|&s;i&s;tence, I &s;hall premi&s;e &s;omething; and fir&s;t, concerning the Gravitation of Water upon Water, and then of Ayr upon Ayr.</P>
<PB N="32" REF="20">
<P>It &s;eems clear, that the upper parts of Water do not actually or &s;en&s;ibly Gravitate or pre&s;s upon the lower parts of Water; They do indeed Gravitate <HI>ad pondus</HI> and Phy&s;ically upon the lower, &s;o as to make the whole hea|vier, but they do not. Gravitate <HI>ad mo|tum,</HI> or &s;en&s;ibly: That which per|&s;wades me hereunto is Rea&s;on and Ex|perience, or Ob&s;ervation.</P>
<P>(<HI>Fig.</HI> 2.) For Rea&s;on, I alledge, that if the upper parts, &s;uppo&s;e the Cube of Wa|ter <HI>C</HI> &s;hould Gravitate &s;en&s;ibly upon <HI>D,</HI> and con&s;equently upon <HI>E,</HI> in the Ve&s;&s;el of Water <HI>A B,</HI> it mu&s;t either be by di&s;placing of <HI>D</HI> and <HI>E</HI> from their po&s;iti|on, and &s;o <HI>C</HI> to &s;ub&s;ide in the place of <HI>D,</HI> and after in the place of <HI>E,</HI> or el&s;e it mu&s;t be by Compre&s;&s;ing of <HI>D</HI> into a &s;hallower &s;pace; but it can be neither of the&s;e, and therefore it cannot &s;en&s;i|bly or <HI>ad motum,</HI> Gravitate upon <HI>D,</HI> and con&s;equently upon <HI>E.</HI></P>
<P>As to the fir&s;t Propo&s;ition, we can|not, that I know of, think of a third; It is true, it hath a Gravitation <HI>ad pon|dus,</HI> becau&s;e it adds the weight of a
<PB N="33" REF="20">Cube of Water to the common weight of the Water, but as to any &s;en&s;ible Gravitation, or Gravitation <HI>ad motum</HI> it is otherwi&s;e.</P>
<P>As to the minor Propo&s;ition, it con|&s;i&s;ts of two Parts; 1. An Exclu&s;ion of the di&s;placing of <HI>D:</HI> 2. An Exclu|&s;ion of its compre&s;&s;ion or contraction in height.</P>
<P N="1">1. It cannot remove <HI>D</HI> from the place it holds, becau&s;e the Cube of Water <HI>C</HI> is of equal weight and &s;olidne&s;s with that of <HI>D;</HI> and it mu&s;t be either a Body intrin&s;ecally or at lea&s;t extrin&s;e|cally heavier than <HI>D,</HI> that mu&s;t make <HI>D</HI> give place to it.</P>
<P>If it be &s;aid that <HI>D</HI> may get out of either &s;ide, and &s;o give way to the pre&s;|&s;ure of <HI>C;</HI> that cannot be, for the Col|lateral or Tran&s;ver&s;al Column of either &s;ide, as &s;trongly compre&s;&s;eth <HI>D</HI> as the Cube <HI>C,</HI> becau&s;e each &s;ide is not only pre&s;&s;ing with its lateral pre&s;&s;ure again&s;t the &s;ides of <HI>D,</HI> But there impends up|on that lateral Column a Cube or Co|lumn, of equal h&egrave;ight with <HI>C,</HI> and pre&s;|&s;eth as hard upon it.</P>
<PB N="34" REF="21">
<P N="2">2. Again, if <HI>C</HI> &s;hould actually and &s;en&s;ibly Gravitate upon <HI>D,</HI> and con&s;e|quently <HI>C</HI> and <HI>D</HI> upon <HI>E,</HI> and &s;o <HI>C</HI> &s;hould &s;ub&s;ide, that which is driven up would po&s;&s;e&s;s the place of <HI>C,</HI> and then that &s;hould &s;ub&s;ide again, and other &s;hould &s;ucceed in its place, and &s;o the Body &s;hould be in perpetual Motion, which is not only contrary to common Sen&s;e and Experience, but to Rea&s;on al&s;o.</P>
<P N="3">3. Again, (which is but a various Explication of the fir&s;t in&s;tance) it is not po&s;&s;ible for a Body of equal weight (&s;uch as <HI>C</HI> is to <HI>D</HI>) to impel or drive out of its place a Body of the &s;ame equal weight, for the re&s;i&s;tance is as &s;trong as the power that &s;hould move it, which nece&s;&s;arily mu&s;t give re&s;t; for if the Cube <HI>D</HI> be driven out of its place unto a higher Superficies, it mu&s;t be driven up by a greater weight than it &s;elf, otherwi&s;e it will never obey it, nor yield to it.</P>
<P>Some therefore finding the&s;e diffi|culties, have re&s;orted to the &s;econd part, namely, That the Cube <HI>D</HI> is compre&s;t into a &s;hallower con&s;i&s;tence: But this can not be neither.</P>
<PB N="35" REF="21">
<P>Fir&s;t, if it be compre&s;&s;ed down|wards; namely, between <HI>C</HI> and <HI>E,</HI> and al&s;o <HI>E</HI> between <HI>D</HI> and the Fund, then it mu&s;t be compre&s;t narrower al&s;o, be|cau&s;e for the rea&s;on before given, the lateral pre&s;&s;ures again&s;t the &s;ides of <HI>D</HI> mu&s;t be as effectual as that upon the upper Ba&s;e of <HI>D;</HI> which would make &s;trange work.</P>
<P>Secondly, Though the quality of Ayr be &s;uch, as it may be capable of Compre&s;&s;ion, yet Water is utterly uncapable of it; if we lay a weight of a hundred pound upon a Ve&s;&s;el of Wa|ter, indeed if it do not compre&s;s the whole Superficies of the Water entire|ly, it will drive it up where it doth not pre&s;s; but if it &s;trictly cover the whole Superficies of the Water, it will never pre&s;s it &s;hallower.</P>
<P>Thirdly, It is more evident to Ex|perience, that the lower parts of the Water are not pre&s;&s;ed by the upper: For fir&s;t, If it &s;hould be &s;o, a Tube of Water, &s;uppo&s;e ten Foot long, filled and clo&s;ely &s;topped at both ends, would break the Gla&s;s, if it lay Horizontally,
<PB N="36" REF="22">or if a reclined Tube were exactly fil|led, yet being &s;et up perpendicularly, it would leave a vacancy, which it will never do, notwith&s;tanding the preten|ded Acce&s;&s;ion of the Gravitation of Ayr to boot. Again &s;econdly, Let any man try it in a Tube of Water of con|&s;iderable length, and put in a little button of Wax, inclo&s;ing a peece of Lead to make it &s;ink, it will &s;ink to the bottom of the Water, rather with &s;ome little degrees of Acceleration, the lower it de&s;cends; which could never be, if the Water were more compact and pre&s;t below than above.</P>
<P>As to Experiments and Ob&s;ervati|ons, it is agreed by all per&s;ons, that have treated of Hydro&s;tatiques, that I know, only one excepted, That if a Solid Body, &s;uppo&s;e of Wood, of equal weight with the like quantity of Water, be placed in Water, it will reft in all Po&s;itions under the Superficies of the Water, which could not po&s;&s;ibly be, if the Water to wards the bottom were more compre&s;&s;ed than it is towards the Superficies: This is agreed by <HI>Archi|medes,</HI>
<PB N="37" REF="22">the Ma&s;ter of Hydro&s;tatiques, in his Book, <HI>De In&s;identibus Humido;</HI> by <HI>Stevin,</HI> in his <HI>Hydro&s;tatical Elements,</HI> Prop. 4. By Mr. <HI>wallis,</HI> Mr. <HI>Boyl,</HI> and others.</P>
<P>Only a late Author, in his <HI>Hydro&s;tati|cal Theorems,</HI> tells us, that &s;uch a Solid will emerge &s;o, that its upper Superfi|cies will be contiguous to the Superfi|cies of the Water; And this he con|cludes, not &s;o much upon his Ob&s;erva|tion or Experience, for ought I can find, as upon this very &s;uppo&s;ition, that the Water below is more compre&s;&s;ed than that above.</P>
<P>It is a difficult matter to find any Solid by its own &s;pecifical uniform weight, to be ju&s;t equal to the weight of a bulk of Water of an equal dimen|&s;ion to it, without application of &s;ome &s;ub&s;idiary &s;upplyes to equal it, which po&s;&s;ibly may make the Experi|ment it &s;elf uneffectual; yet upon the be&s;t tryal I could make by &s;uch &s;ub&s;i|diary applications, I rather find &s;uch an Equiponderating Solid rather to be apt to &s;ub&s;ide to the bottom, than emerge to the top.</P>
<PB N="38" REF="23">
<P N="2">2. Again, the next Experiment which I &s;hall mention, &s;hall be that of the &s;ame Author, in his &s;eventeenth Experiment, wherein, if I under&s;tand him aright, he contradicts what he had delivered in his fifteenth Theorem: <HI>viz.</HI> <Q><HI>If a Gla&s;s bubble with a long &s;tem turned up, heated, and then the &s;tem Her|metically &s;ealed and depre&s;&s;ed into the Wa|ter, by a convenient weight of Lead, and the Bubble tyed with a &s;tring to the Beam of a Ballance, with &s;o much weight as might counterpoi&s;e the Bubble, then the &s;tem bro|ken with a Forcept, whereby the Water entred and half filled the Bubble, the Bub|ble &s;ub&s;ided and required an addition of a farther counterpoi&s;e of</HI> 4 <HI>Drams and</HI> 38 <HI>Grains, to reduce it to an</HI> Equilibrium, <HI>then the Bubble taken out, and the Water driven out of it, weighed</HI> 4 <HI>Drams and</HI> 30 <HI>Grains:</HI></Q> This in&s;tance being given by a worthy Per&s;on, to prove, that Water weighs in Water: But the Author, in an&s;wer thereunto, clearly evinceth, that the Water in the Bubble is &s;up|ported by the &s;ubjacent Water, and concludes evidently thereupon, that
<PB N="39" REF="23">Water weighs not in Water.</P>
<P N="3">3. Again, if Water &s;hould &s;en&s;ibly Gravitate upon Water, it mu&s;t as &s;en|&s;ibly Gravitate upon any Body &s;ub|jected in it, e&s;pecially if it be at the Ba&s;e or fund of the Water: But the Experience of divers, of the agility of Fi&s;h of a great breadth, lying at the bottom of the Water, and infinite more, do &s;ufficiently evince, that the weight of the &s;uperior parts of Water Gravitate not upon the inferior parts, with any &s;en&s;ible pre&s;&s;ure, for if it &s;hould, it mu&s;t of nece&s;&s;ity Gravitate upon the interjacent Water, lying be|tween the uppermo&s;t Cube and the Bo|dy; and if it &s;hould do &s;o, if mu&s;t con|&s;iderably Gravitate upon the &s;ubjacent Body.</P>
<P>But this <HI>Non-gravitation of Water upon Water, or upon &s;ubjected Bodies, and the rea&s;ons thereof,</HI> I have el&s;ewhere examined.</P>
<P>(<HI>Fig.</HI> 3.) An excellent Per&s;on, in the fir&s;t, &s;econd, and la&s;t Chapters of <HI>Hy|dro&s;tatical Paradoxes,</HI> hath endevoured to prove the actual Gravitation of the
<PB N="40" REF="24">&s;uperior parts of Water upon the infe|rior, by three in&s;tances, <HI>viz.</HI> If in the third Figure, the Ve&s;&s;el <HI>AB</HI> be filled with Water unto the Superficies <HI>c d,</HI> and then the Tube be by &s;uction filled with Oyl of Turpentine (a Body ligh|ter than &s;o much Water) be &s;topped nimbly at the top, whereby the Oyl remains &s;u&s;pended, and then the lower open end be immer&s;ed in the Ve&s;&s;el of Water unto any depth, &s;uppo&s;e <HI>H,</HI> and then the Finger be removed from <HI>G,</HI> the Super&s;icies of the Tube, the Oyl will be kept up to &s;uch a height as may counterpoi&s;e the like Column of Water in the Ve&s;&s;el; and if it be immer&s;ed lower, the Oyl will ri&s;e in the Cube con&s;iderably higher, and if it be lifted up higher, nearer to the Superficies of the Water, the Oyl will &s;ub&s;ide lower, and di&s;charge part of it &s;elf into the Water, becau&s;e then the like Column of Water in the Ve&s;&s;el grows &s;horter, and hath a le&s;s counterpoi&s;e to the Co|lumn of Oyl in the Tube, which he concludes to be a concludent evidence of the various degrees of Gravitation
<PB N="41" REF="24">of the Water upon the various imagi|nary Superficies thereof. The &s;econd in&s;tance is like it, namely, That if the &s;ame Ve&s;&s;el were filled with Oyl to the Superficies <HI>C D,</HI> and the Tube <HI>g</HI> filled three or four Inches with Water by &s;uction, and the upper end <HI>g</HI> nimbly &s;topt with the Finger, and then the lower end <HI>H</HI> immer&s;ed in the Oyl, the deeper it is immer&s;ed, the higher the Superficies of the Water in the Tube will remain &s;u&s;tained, and the nearer it is brought to the Superficies, the lower it will &s;ub&s;ide, by rea&s;on of the various degrees of Gravitation of the Oyl in &s;everal imaginary Superficies; though at the highe&s;t elevation of the Tube of Oyl, in the fir&s;t in&s;tance, the Oyl, in re&s;pect of its le&s;s Gravity than Water, will &s;it &s;ome what higher in the Tube than the Superficies of the Wa|ter; and the Water in the Tube, in the &s;econd in&s;tance, will &s;it lower than the Superficies of the Oyl, becau&s;e excee|ding it, quantity for quantity in &s;peci|fical Gravity. 3. The third is that of the valve, which deeply immer&s;ed
<PB N="42" REF="25">in Water, the cover of the value will be &s;u&s;tained by the Gravitation of the Water, with a con&s;iderable weight ap|pended to it.</P>
<P>But it &s;eems to me, that the&s;e Expe|riments concludes nothing to this bu|&s;ine&s;s; but only evidence a re&s;i&s;tence of the Water to that Body which will rai&s;e its Superficies. For it is appa|rent, that there is required a pre&s;&s;ure, or force, to rai&s;e the Body of Water to a higher Superficies, exceeding the weight of &s;o much Water as is &s;o im|pelled higher than before, or at lea&s;t equal to it.</P>
<P>Now the pre&s;&s;ing down of the Tube of Oyl into the Water, or the Tube of Water into the Oyl, rai&s;eth the Super|ficies of the Water or Oyl &s;o much as the Tube is impre&s;&s;ed into the Water, namely, a quantity of Oyl or Water in the Ve&s;&s;el, equal to the Body impre&s;|&s;ed and immer&s;ed in it, is rai&s;ed there|by, and put out of its former place, which it contents again&s;t, by a Reni|tence re&s;i&s;tence, or contrary pre&s;&s;ure; and as the le&s;s of the Tube is immer&s;ed,
<PB N="43" REF="25">the le&s;s Liquor in the Ve&s;&s;el is moved up; &s;o the more of that Body is im|mer&s;ed, the more is pre&s;&s;ed up, and con&s;equently, the greater pre&s;&s;ure is made upon the Water, the lower it is immer&s;ed; becau&s;e it takes up more room in the Water, and a greater force is thereby exerci&s;ed, to the elevation of a greater quantity of Water; and that Water, the more it is, hath the more accidental weight, or rather, re&s;i&s;tence, again&s;t that force which thus rai&s;eth it up above its common &s;uperficies, which before it obtained.</P>
<P>And that this is the true rea&s;on of it, and not the various Gravitations of the &s;uperior parts upon the inferior, &s;eems evident by this one in&s;tance, which becau&s;e it will be u&s;eful hereaf|ter, upon other occa&s;ions, I &s;hall here in&s;ert more largely, though the thing be commonly known.</P>
<P>I filled a Tube of Lead of &s;ix Inches Diameter, and four Foot deep, and clo&s;e at the bottom with Water; And took a Porringer of Pewter, five Inches Diameter, and about two Inches deep,
<PB N="44" REF="26">and filled it with leaden Shot, and pou|red Water into it, to fill up the chinks, and making four holes, I &s;u&s;pended it with a Packthrid, like the Di&s;h of a pair of Scales, and exactly weighing it, and the Shot, Thred, and Water, it weighed all exactly 78 Ounces, wan|ting &frac18; of an Ounce; then &s;u&s;pending the Di&s;h with a Packthrid, to the end of the beam, I &s;et it down 40 Inches deep into the Water, below its Super|ficies, and it lo&s;t its weight, by the re&s;i&s;tance and cra&s;&s;itude of the <HI>medium, viz.</HI> the Water <HI>9</HI> Ounces &frac12; of its weight in Ayr; and &s;o weighed 68 Ounces, and near about &frac12; of an Ounce; and ju&s;t the &s;ame weight it held, when rai&s;ed 15 Inches, when rai&s;ed 28 Inches, though it was then within 12 Inches of the Superficies; but at la&s;t, when I rai&s;ed it 12 Inches higher, &s;o that the Superficies of the weight was equal with it, and yet it lo&s;t not above &frac18; of an Ounce; which I decrement, was, as I think, becau&s;e po&s;&s;ibly the four &s;trings that &s;u&s;tained it were not now under Water.</P>
<PB N="45" REF="26">
<P>What then is the rea&s;on why, when the Tube of Oyl or Water is &s;unk lower, the pre&s;&s;ure of the Water is un|equal? and why in this in&s;tance, the weight of the Di&s;h is no more charged with the weight of the Water, at 40 Inches, than when ju&s;t even with the Superficies of the Water: I &s;ay it is not the Gravitation of the &s;uperior parts of the Water upon the inferior, for then my weight of 5 Inches Di|ameter could never keep the &s;ame weight at 40 Inches depth of Water, at 12 Inches depth, and ju&s;t at the Su|perficies; but the true rea&s;on is, becau&s;e in the weight of the Porringer and Shot, being the &s;ame bulk at 40 Inches deep, as at the very Superficies, drives up no more Water out of its place at one &s;tation, than another; namely, a bulk commen&s;urate to the bulk of the Porringer, Shot, and included Water, which is the &s;ame, both at the fund of the Tube, and when its Superficies is contiguous to the Superficies of the Water: But in the in&s;tances of the Tube, if it were &s;uppre&s;&s;ed an Inch
<PB N="46" REF="27">Diameter, when it is immer&s;ed an Inch its <HI>potentia,</HI> lifts up but a part of Water commen&s;urate to that Inch; and there|fore the re&s;i&s;tence, or Renitence between the Tube, and the Water, is but little; but when it is immer&s;ed ten Inches, there is ten times more Water driven up, and therefore the Renitence is the greater, and impels the Liquor included in the Tube the higher; But this con|cerns nothing the weight of Water in its quiet con&s;i&s;tence: His other Expe|riments, in order to the proof of the Gravitation of Water upon Water, I &s;hall con&s;ider in the fifth Chapter.</P>
</DIV2>
<DIV2 N="4" TYPE="chapter">
<PB N="47" REF="27">
<HEAD>CHAP. IV.</HEAD>
<HEAD TYPE="sub"><HI>Concerning the Gravitation of the Ayr upon Ayr, or any &s;ubjected Bodies in it.</HI></HEAD>
<P>THe Que&s;tion in hand concernes not Ayr put out of its ordinary texture, but touching the free Ayr, wherein Men and Animals live and breath.</P>
<P>And now to &s;tate this Que&s;tion a|right, we mu&s;t con&s;ider, 1. What the Que&s;tion is not, and 2. What the Que|&s;tion is.</P>
<P N="1">1. The Que&s;tion is not whether Ayr compre&s;&s;ed and thru&s;t together, hath a weight in it that may put it into a con|&s;iderable Gravitation upon other Ayr, either not compre&s;&s;ed at all, or le&s;s compre&s;&s;ed; for it &s;eems very proba|ble by the Experiments of the&s;e Ex|cellent Men, <HI>Mer&s;ennus, Shottus,</HI> Mr. <HI>Boyl,</HI> and others, that have &s;et them|&s;elves unto tryals, in order to this in|quiry,
<PB N="48" REF="28">that &s;uch a Gravitation may and doth happen by the compre&s;&s;ion of Ayr in AEolipiles and Wind-guns, that &s;uch Ayr may have a pretty evident prepon|deration to &s;o much free and common Ayr.</P>
<P N="2">2. Neither is it the Que&s;tion, whe|ther there may not be, or are not inter|&s;per&s;ions of Vapours <HI>Effluvia,</HI> and <HI>Efflu|via,</HI> or other <HI>Moleculoe</HI> even in the free and common Ayr, that con&s;idered in them&s;elves, have a preponderation even to the Ayr it &s;elf; for although the &s;trict intermingling, interweaving, and contiguation of &s;ome Vapours and <HI>Effluvia,</HI> gro&s;&s;er and weightyer than the Ayr it &s;elf, may enable the Ayr to &s;u|&s;tain and bear up many of the&s;e gro&s;&s;er Bodies, (as Water oftentimes &s;u&s;tains minute Bodies, or Gravels of Sand &s;pe|cifically heavier than the Water) yet we every day &s;ee, that if the&s;e portions of inter&s;per&s;ed Vapours or <HI>Effluvia,</HI> grow too heavy for the Ayr to &s;u&s;tain them, they are precipitated out of it, and di&s;charge them&s;elves upon the Earth, as we &s;ee in Hail, Snow, Rain,
<PB N="49" REF="28">and Mi&s;ts. 3. Neither is the Que&s;tion, whether a portion of the free Ayr, &s;epa|rated and disjoyned from all commu|nication with the foreign Ayr, hath any Gravitation or no, for it &s;eems to me, that it may have, by &s;uch a &s;eparation an actual Gravitation, which is not by rea|&s;on that it acquires any new quality or acce&s;&s;ion of weight, than it had before, but by rea&s;on of &s;uch &s;eparation it doth <HI>Removere prohibens</HI> of its actual Gravita|tion; namely, the contignation that it hath with the common Ayr, into and with which it was in continuity, it was interwoven, and that little incon&s;iderable Gravitation that it natu|rally and &s;imply con&s;idered hath, is overmatched and broken by tho&s;e inter|veining Filaments of the re&s;t of the Ayr, with which it is in continuity.</P>
<P>And therefore I do think, that if Ayr of the &s;ame con&s;i&s;tence with the Ayr we live in, were freely let into a Bladder, which we will <HI>per impo&s;ibile</HI> &s;uppo&s;e to be de&s;titute of all weight, &s;uch a Bladder of Ayr, thus filled, (though without the help of <HI>inflation,</HI>
<PB N="50" REF="29">by our <HI>longes,</HI> which mu&s;t needs carry with it &s;ome fuliginous Ingredients;) I &s;ay, &s;uch a Bladder of Ayr would &s;ub|&s;ide in the &s;ame common Ayr out of which it was taken, and would Gravi|tate upon the Ballance, more than the like quantity of free and open Ayr incumbent upon the other Ballance.</P>
<P>Nay farther I dare adventure to &s;ay, That if we could &s;uppo&s;e a Tube, open at both ends, &s;o long, as to reach from the top of the Atmo&s;phere, unto this Earth, &s;uch an included portion of Ayr, &s;evered from communion with the Atmo&s;phere, would have &s;ome Gravita|tion more con&s;iderable perchance, than we have ever felt from the open Ayr.</P>
<P>For I do much attribute the exclu|&s;ion of all &s;en&s;ible Gravitation of the free Ayr, to that mutual interweaving of the Filaments of Ayr one into ano|ther, like a va&s;t Net, with &s;mall Ma&s;hes or <HI>inter&s;titia,</HI> filled gradually with parts more and more &s;ubtil; and this contig|nation &s;u&s;tains and keeps the parts of it from that &s;eparation, that otherwi&s;e
<PB N="51" REF="29">the interpo&s;ition of a gro&s;&s;er body would intercept: And although Wa|ter, in re&s;pect of its weight and texture, be more &s;ubject to disjoyn from the re&s;t of its body, than Ayr is, we &s;hall find in the next Chapter &s;omewhat Analo|gous to this, even in a con&s;i&s;tent Body of Water.</P>
<P N="4">4. Neither is it the Que&s;tion, whe|ther even the free Ayr it &s;elf may have &s;ome intrin&s;ique Gravity, though ad|mirably little and incon&s;iderable; for if we do &s;uppo&s;e the compre&s;&s;ion of divers Particles of Ayr may render that compre&s;&s;ed Body of Ayr &s;en&s;ibly hea|vy, we may not wholly exclude tho&s;e Particles from all kind of Gravity be|fore compre&s;&s;ion, for no weighty Body can ari&s;e from the coalition of &s;uch parts as had no manner of Gravity before.</P>
<P N="5">5. Nay, yet farther, the Que&s;tion is not, whether as the free Ayr hath &s;ome intrin&s;ique Gravitation; &s;o neither is it the Que&s;tion, whether this free Ayr hath not &s;ome, though very incon&s;ide|rable mea&s;ure of actual Gravitation;
<PB N="52" REF="30">it is not impo&s;&s;ible but it may have &s;ome, though &s;carce perceptible to &s;en&s;e, notwith&s;tanding all the inter|&s;pertions and mixtures of Vapours and <HI>Effluvia</HI> from the Earth and Water.</P>
<P>But the Que&s;tion is, whether the free and common Ayr, wherein we live, which is commonly called At|mo&s;phere, extending upwards about &s;even Miles or more, hath any &s;en&s;ible actual Gravitation upon the lower World. 2. Admit it have, whether any determinate portion of that Atmo|&s;phere, as a Column or inverted Cone, for the purpo&s;e, of &s;ix Inches &s;quare at the Ba&s;e, hath any actual Gravitation upon the &s;ubjected Ba&s;e, upon which it is &s;uppo&s;ed to re&s;t. 3. Admit it hath, whether that Gravitation be of any con&s;iderable, and of what moment.</P>
<P>Before I come to di&s;cu&s;s the Que&s;ti|ons them&s;elves, it will be nece&s;&s;ary to repeat &s;omewhat that I have before &s;aid, touching the proportion of Gra|vitation, that is alloted to a portion of, for in&s;tance of &s;ix Inches &s;quare of the Atmo&s;phere, when it pertingeth near to the Superficies of the Earth.</P>
<PB N="53" REF="30">
<P>A Cube of Water, &s;ix Inches &s;quare, contains 216 &s;quare Inches, and upon the exact Calculation of tho&s;e that have tryed it, weighs ju&s;t &s;even Pounds, and a Cube of twelve Inches &s;quare of Water weighs 56 Pounds.</P>
<P>A Cube of Quick&s;ilver weighs four|teen times as much as the like quantity of Water, though <HI>Mer&s;ennus,</HI> and &s;ome others, nearer to the truth, com|pute it to be thirteen and &frac12;; but I will make my Calculation by fourteen, to avoid Fractions.</P>
<P>The con&s;equence whereof will be, that a Cube of &s;ix Inches &s;quare of Mercury, will weigh 98 Pounds, which is fourteen times as much as the like Cube of Water.</P>
<P>The con&s;equence whereof is, that fourteen &s;uch Tubes of Mercury weighs 1372 pound.</P>
<P>In the <HI>Torricellian</HI> Experiment, the Mercury is &s;u&s;tained to the height of 29 Inches &frac12;; to avoid Fractions, let us reckon it 30 Inches, be the Column never &s;o large.</P>
<P>If the Column of Mercury be &s;ix
<PB N="54" REF="31">Inches &s;quare at the Ba&s;e, then there will be five &s;uch &s;quare Cubes of Mer|cury in that Column will weigh 490 Pounds: According to the late Phi|lo&s;ophy, this Column of Mercury is counterpoi&s;ed with a Column of the Atmo&s;phere of &s;ix Inches &s;quare, and extending from the re&s;tagnant Mercu|ry to the upper &s;urface of the Atmo|&s;phere.</P>
<P>And con&s;equently, this Column of Ayr or Atmo&s;phere, doth actually gra|vitate with a weight of 490 Pounds, upon the re&s;tagnant Mercury, and real|ly and actually weighs as much as that comes to; and con&s;equently, when I hold a Trencher in my hand of &s;ix In|ches &s;quare, there is incumbent upon it 490 Pound weight of Ayr, though there be found a help in that ca&s;e to &s;upport it, by the recoyling Column of Ayr, commen&s;urate to it; whereof in its due place.</P>
<P>And this is the &s;uppo&s;ition I contend again&s;t in this paper, <HI>viz.</HI> that 1. The whole Body of the Atmo&s;phere hath no con&s;iderable Gravitation either upon its
<PB N="55" REF="31">own parts, or upon the &s;ubjected Body of the Terre&s;trial Globe, much le&s;s &s;uch a prodigious Gravitation as is here &s;uppo&s;ed. 2. If it had, yet any given portion or Column of the At|mo&s;phere, hath no &s;uch Gravitation.</P>
<P>Touching the Gravitation of the whole Atmo&s;phere in general, upon the Terre&s;trial Globe entirely, I &s;hall not &s;ay much, becau&s;e it is not capable of Experiment, only my rea&s;on and &s;en&s;e &s;ugge&s;ts it to me, that it is neither evi|dent nor likely to be of &s;o va&s;t a Gra|vitation as the late Philo&s;ophers affirm.</P>
<P>Fir&s;t, I confe&s;s I am none of tho&s;e Adepts in Philo&s;ophy, that can tell us how to &s;olve all the effects in Nature, without recour&s;e to the infinite Wi&s;|dom, Power, and Goodne&s;s of the Glo|rious God, who certainly knew better how to frame the World, and fix the Laws of Nature, than the wi&s;e&s;t of Men or Angels. I mu&s;t confe&s;s, I know not how to re&s;olve the rea&s;on of the Motion of weighty Bodies downward nor why or how either the Sun holds his regular Motion, if the Hypothe&s;is
<PB N="56" REF="32">of <HI>Ptolemy</HI> be true, or why the Earth, as other Planetary Bodies, holds its re|gular Motion, if the Sy&s;teme of <HI>Coper|nicus,</HI> and <HI>Galilaeus,</HI> be true, and a thou|&s;and &s;uch in&s;tances; but into the primi|tive di&s;po&s;ition and ordination of the Mo&s;t Wi&s;e, Powerful, and Soveraign Lord and Maker of the World, who hath fixed the Order and Law of Na|ture, by his Soveraign <HI>Fiat,</HI> with the mo&s;t exact accommodation of it to the concerns of the Univer&s;e, and all the parts thereof, and with mo&s;t in|comparable Congruity. This Sove|raign Architect, that hath made all the parts of this <HI>Mundus a&s;pect abilis</HI> in Or|der, Weight, and Mea&s;ure, and de&s;igned the Earth and Ayr, for the habitation and u&s;e of Men, and all other breathing Animals, and likewi&s;e for Vegetables, hath &s;o ordered and dige&s;ted the texture of the Ayr, that the inferior part is more gro&s;s than the &s;uperior, and fit|ted for nouri&s;hment and re&s;piration; the upper parts more &s;ubtil, and pure, and light, and de&s;tined to other u&s;es, hath ballanced the Ayr, &s;o that the more
<PB N="57" REF="32">light and &s;ubtil parts are inclinable per|chance, more to a&s;cend; and the lower parts gradually more laden with Parti|cles of a gro&s;&s;er allay, and &s;o po&s;&s;ibly thereby inclinable to &s;ub&s;ide; and he hath connected the more &s;ubtile, and the more Feculent parts thereof, &s;o together, that they hold an <HI>Equilibrium</HI> as a &s;tate and po&s;ture more &s;erviceable to the ends and u&s;es he de&s;igned for it, and for which they &s;erve: The procee|ding of this Soveraign Architect in the Frame of this great Building of the Univer&s;e, not being like to the Architecture of men, who begin at the bottom; but he began at the Roof, and Builded downwards, and in that proce&s;s, &s;u&s;pended the inferior parts of the World upon the &s;uperior. But this kind of rea&s;oning, I know, is not grate|ful to the palate of the pre&s;ent Philo&s;o|phers; I therefore proceed.</P>
<P>Secondly, Therefore I &s;ay, that the common appearances of the World, &s;o far as they are obvious to our common &s;en&s;es, contradicts this immen&s;e, nay, or any con&s;iderable Gravitation of the
<PB N="58" REF="33">Atmo&s;phere upon &s;ubjected Bodies; It is hardly conceptible, how Birds could rai&s;e them&s;elves upon their wings, and keep them&s;elves in free Ayr, if a bur|then perchance of above 1000 pound weight &s;hould lie upon their Wings and Bodies; it were not po&s;&s;ible for me to breath, to walk, to &s;tand upon my Feet, if at every time I open my Mouth, a Column of Ayr of three hundred pounds weight were pre&s;&s;ing into it, it would tare open the valves of my <HI>Larinx,</HI> and blow up my Stomach and Intrals, like a Bladder, and break my Ribs, if it had an admi&s;&s;ion; and if it had not the circumjacent pre&s;&s;ure of the Ayr, would pre&s;s me to death: The&s;e and the like in&s;tances render this prodigious Gravitation of the Ayr incredible to us vulgar Souls, that are apt to creditour &s;en&s;es.</P>
<P>But I very well know, that the&s;e will be &s;aid to be vulgar common pla|ces, and that they have many hand|&s;ome Solutions of the&s;e common diffi|culties.</P>
<P>And it is true, I very well know,
<PB N="59" REF="33">they have colourable Solutions for tho&s;e &s;en&s;ible occurrences, as the &s;up|po&s;ed counterpoi&s;e of included Ayr, and of the recoyling Columns of Ayr; which I &s;hall in due time con&s;ider.</P>
<P>But I do reply, that though the&s;e common in&s;tances perchance amount not to demon&s;trations of the untruth of the Hypothe&s;is, yet they do require a very great and very clear evidence to encounter even tho&s;e vulgar experien|ces; and therefore, if any Solutions offred of them, are not perfectly con|cludent, but &s;trained, and the in&s;tan|ces they give in their favour, are capa|ble of any other Solution, than this which is &s;o vi&s;ibly and apparently con|trary to our &s;en&s;e; &s;uch Solutions and &s;uch in&s;tances are too weak and impo|tent to build &s;uch uncouth conclu&s;ions upon.</P>
<P>Thirdly, Therefore I &s;ay, there is not any one in&s;tance or experiment, that ever I yet heard of, for the evincing of this imaginary Gravitation of the free Ayr, but is readily capable of a more &s;utable Solution more adequately
<PB N="60" REF="34">fitted to the <HI>Phaenomenon,</HI> and le&s;s in|cumbred with difficulties than this new Solution, by the Gravitation and Elatory of the Ayr. I &s;hall refer my &s;elf herein to Mr. <HI>Linus</HI> his Tract <HI>De In|&s;eperabilitate Corporum:</HI> And <HI>Honoraly Fabri,</HI> in the 6^t^h of his late <HI>Philo&s;ophical Conferences,</HI> wherein all the in&s;tances given from the <HI>Magdeburg</HI> Engin, and the <HI>Engli&s;h</HI> Ayr Pump, and particularly the <HI>Torricellian</HI> Experiment, are &s;uffi|ciently and much more &s;atisfactory and naturally &s;olved, without recour&s;e to this imaginary Weight or Spring of Ayr.</P>
<P>And there are above an hundred Ex|periments of this kind and nature, which can never by this &s;olution be ex|plicated (without intolerable torture of them) &s;ome in&s;tances whereof we &s;hall in due time remember.</P>
<P>But omitting more that may be re|plyed in general to the common Gra|vitation of the Ayr; I &s;hall more par|ticularly and clo&s;ely apply my &s;elf to the &s;econd.</P>
<P>2. Therefore, admitting it were
<PB N="61" REF="34">po&s;&s;ible to &s;uppo&s;e the whole Body of the Atmo&s;phere might Gravitate upon the Earth in general, yet no one par|ticular portion of the free and common Ayr, impending upon any one determi|nate Superficies, can at all or at lea&s;t can &s;en&s;ibly or con&s;iderably Gravitate upon any determinate <HI>Ba&s;is.</HI></P>
<P>And the rea&s;on &s;eems to me to be this, becau&s;e although we &s;hould admit a con&s;iderable Gravity of a portion of Ayr taken, divided and &s;eparated as one intire &s;eparate Gro&s;s Body (as in a Bladder, a Gla&s;s Bubble, or the like) &s;o that it partakes of the common quality of heavy Bodies, yet there is a peculi|ar pre&s;&s;ure or Gravitation belonging to this &s;ubtile Fluid Body, which hath its lines of direction every way within the compa&s;s of its own extream Superficies, whereby that perpendicular Gravita|tion, which is common to all Bodies, is corrected, abated, and in a great mea|&s;ure &s;u&s;pended. 2. Becau&s;e that if there were no &s;uch allay given to its common perpendicular Gravitation, by its proper Motion or Gravitation of its
<PB N="62" REF="35">own; yet the Ayr being one continued Body, and &s;o interwoven and mortai&s;ed as it were, one part in another, the other parts of the Ayr that are conti|guous every where to the Earth, do &s;u&s;tain and bear it up, like the &s;ides of an Arch, from any &s;en&s;ible pre&s;&s;ure or Gravitation upon any determinate or particular Body, that is within the com|pa&s;s of its pre&s;&s;ure; as I have el&s;ewhere inforced the Argument in relation to the Gravitation of Water upon &s;ub|jected Bodies, narrower than the com|mon Ba&s;e that &s;upports &s;uch Water.</P>
<P>And although the Ayr hath an in|termingling with it of Vapours and Terre&s;trial and Aqueous <HI>Efftuvia</HI> hea|vier than it &s;elf; yet they are &s;o inter|woven in the very Webb and texture of the Ayr, that it &s;upports many of them, and tho&s;e that are too heavy for it, or much di&s;united and &s;eparate from it, are precipitated upon the Superficies of the Earth, and the Ayr di&s;charged of them, as in Rain, Snow, Hail, &s;ub|&s;iding Gravel Sand, &amp;<HI>c.</HI></P>
<P>And although the in&s;tance that I
<PB N="63" REF="35">am now giving, is more proper for the next Section, yet it is in &s;ome kind &s;u|table for the explication of what I intend.</P>
<P>Of all hands it is agreed, that the Water, though a Fluid Body, is, &s;ome &s;ay, thirteen hundred times heavier than the like portion of Ayr; others, that it is a thou&s;and times heavier; they that &s;peak lea&s;t, &s;ay it is above nine hundred times heavier than Ayr: And it is obvious to any that attends it, that there is not the &s;ame &s;trict Cohe&s;ion of one part of Water with another, as is of one part of Ayr with another, un|le&s;s divided by a more firm and &s;table Body then it &s;elf: And therefore there is far more rea&s;on, that one part or Column of Water in its con&s;i&s;tency &s;hould Gravitate upon a &s;ubjected Body, than there is, that a Column of Ayr &s;hould in the free and open Ayr, Gravitate upon a body &s;ubjected to it; And yet it will be found, that in <HI>libera aqua,</HI> that Gravitation that it exerci&s;eth upon a Body &s;ubjected to it, and capable of it, is not above one half &s;o much
<PB N="64" REF="36">as the weight of &s;uch a Column of Water, divided and &s;eparated from the common con&s;i&s;tent Water.</P>
<P>It is true, I had not &s;o dextrous a Me&s;&s;enger, to make the Experiment in the bottom of the Sea, or 20 Fathom within Water, as <HI>Dromo</HI> is Poetically related to have done, though I believe he never made that tryal: But I will give an account of what I have tryed and found.</P>
<P>(<HI>Fig.</HI> 4) I took a Gla&s;s Siphan of a quarter of an Inch Diameter, the lon|ger legg 32 Inches, the &s;horter 8. Inches long, open at both ends.</P>
<P>I filled the &s;hort legg with Mercury, which accordingly as it mu&s;t, ro&s;e to 8 Inches high in the longer legg; and then &s;topping the &s;horter legg with my Finger to avoid any violent pre&s;&s;ure by the fall of the Water upon the Mercury, I then filled the longer legg to the top with Water, and gently removing my Finger from the &s;horter legg, to avoid too violent an Ex&s;ilition of the Mercury, I found the Mercury to &s;ub&s;ide in the longer legg two Inches and a quarter,
<PB N="65" REF="36">and as much driven out of the &s;horter legg, by the acce&s;&s;ion of the weight of 24 Inches of Water in the longer legg, (which I confe&s;s is &s;omewhat le&s;s than the proportion of weight between Wa|ter and Mercury; wherein, according to an exact calculation, 28 inches of Water counterpoi&s;eth 2 Inches of Mer|cury. But then emptying the Water and Mercury out of the Tube, I again filled up the Tube with Mercury, to 8 Inches in both leggs, namely to the top of the &s;hort legg.</P>
<P>And then filling a gla&s;s Tube, of a|bout three Inches diameter, and 32 In|ches long, with Water, I immer&s;ed the Syphon with the Quick-filver to the bottom of the greater Tube full of Wa|ter. And although the column of Wa|ter in the great Tube, impending upon the orifice of the &s;horter legg, was full 24 Inches, yet it drew down the Mer|cury in the &s;hort legg, and rai&s;ed it in the longer legg, empty of Water, only one Inch, and no more, whereby it did ri&s;e in the longer legg to 9 Inches, and &s;ub&s;ided in the &s;horter to 7 Inches,
<PB N="66" REF="37">as I could ea&s;ily perceive through the great Tube, by a Scale of Inches, and quarters, fitted to each leg of the Syphon.</P>
<P>I then tried it doubly, <HI>viz.</HI> pouring in the Water into the longer legg of the the Syphon, whereby the &s;ubjacent Mer|cury &s;ub&s;ided in the longer legg two Inches, and as much thereof driven out of the &s;horter legg, and then immer&s;ed the Syphon into a gla&s;s-ve&s;&s;el, 32 Inches deep, filled with Water; the Mercury thereupon &s;ub&s;ided in the &s;hort legg &s;omewhat neer an Inch, and no more, and accordingly impelled up the Mer|cury and incumbent Water in the lon|ger legg neer an Inch: whereby it ap|pears, that there was no <HI>AEquipondium</HI> between the pillar of Water included in the Tube, and the imaginary pillar of Water in the open ve&s;&s;el.</P>
<P>And in this experiment I mu&s;t re|member, that the orifice of the &s;horter legg of the Tube, and the legg it &s;elf, was of &s;omewhat a larger diameter than the longer legg; and that might give &s;ome advantage to the pre&s;&s;ure of the Water in the ve&s;&s;el upon the &s;horter
<PB N="67" REF="37">legg. But notwith&s;tanding that advan|tage, the gravitation of the external Water, or any imaginary column there|of was not half &s;o much as the gravita|tion of the Cylinder of Water included in the Tube; which is &s;ufficient to con|vince the mi&s;take of tho&s;e that a&s;&s;ign an equal pre&s;&s;ure to an imaginary column of free Air or Water, with an equal column of Air or Water that entirely pre&s;&s;eth upon the Mercury, and hath no other circumjacent ba&s;e to lean upon.</P>
<P>And it is to be noted, that although, as I have &s;aid, a Cylinder of two Inches of Mercury doth really counterpoi&s;e a Cylinder of 28 Inches of Water, of the &s;ame diameter, yet in this in&s;tance of the Syphon, 24 Inches of Water drew down two Inches of Mercury, and rai|&s;ed as much out of the &s;horter legg. And the rea&s;on &s;eems to be, becau&s;e the Mer|cury being <HI>in aequilibrio,</HI> was more capa|ble of a &s;en&s;ible pre&s;&s;ure by a le&s;s quan|tity of Water in this <HI>libra naturalis,</HI> than it would be, if both were weighed in their gro&s;s con&s;i&s;tence in an arti&s;icial Scale.</P>
<PB N="68" REF="38">
<P>And the rea&s;ons why the pre&s;&s;ure through the Tube, is &s;tronger than the pre&s;&s;ure by the open ve&s;&s;el of Water, are the&s;e: 1. Becau&s;e in the Tube the Water included had no communion with any open or free Water, nor had any &s;u&s;tentation thereby, but in the com|mon Water there is a communication and mutual &s;u&s;tentation of one part by another. 2. And principally becau&s;e when in the Tube the Water had no other Ba&s;e but the Mercury, to which it was commen&s;urate, and therefore &s;in|gly, and entirely, and adequatly pre&s;&s;ed it. But the Water in the ve&s;&s;el had ano|ther Ba&s;e circumjacent to it, namely the bottom of the ve&s;&s;el, from which it was built like an Arch over the &s;hort legg of the Mercury, whereby the weight, pre&s;&s;ing upon the Mercury, was broken, abated, and intercepted. For Water will find the lowe&s;t Ba&s;e for its re&s;t.</P>
<P>And &s;urely if this be true in Water, as upon more than one tryal I found it, it will be much more &s;o in the open Air, which will much di&s;order the whole <HI>hy|pothe&s;is</HI>
<PB N="69" REF="38">of the Gravitation of the Air, and tho&s;e very &s;ubtle and fine Conclu|&s;ions that are &s;pun out of it, and built upon it.</P>
<P>But I would not be mi&s;taken, as if I meant that the Column of 24 Inches of free Water did gravitate upon the ori|fice of the &s;horter legg of the Syphon, to the weight of neer an Inch of Mercury, for That is wholly contrary to my Sup|po&s;ition: but only I hereby &s;hew the great di&s;proportion of the appearing Gravitation of Water, where it hath no lower nor other Ba&s;e upon which it leans, but only the body of the Mercu|ry, and where it hath another or lower Ba&s;e upon which it leans.</P>
<P>For in this in&s;tance of the Syphon, there is another rea&s;on of the Gravita|tion of the free Water upon the cavity of the &s;horter legg of the Syphon: for here the pre&s;&s;ing or keeping down of the body of the Syphon into the free Water, di&s;placeth and rai&s;eth up a por|tion of Water an&s;werable to the bulk of the whole convex Superficies of the Syphon, which is far greater than its
<PB N="70" REF="39">cavity, and that Water &s;o diplaced doth indeed pre&s;s upon the Tube that di&s;placeth it; and becau&s;e it can find no part yeilding to its pre&s;&s;ure but the orifice of the &s;horter Tube, it pre&s;&s;eth there in &s;uch proportion, as the whole bulk of the Water &s;o lifted up by the immer&s;ion of the Syphon, bears to about an Inch of included Mercury, and 24 Inches of the Water included in the Tube. But of this more di&s;tinctly and exactly, when I come to examin the rea&s;on of the Valve.</P>
<P>2. But having thus offered my rea|&s;ons again&s;t this prodigious Gravitati|on of the imaginary Aery Cylinders, I &s;hall proceed to &s;ome plain and home<GAP DESC="illegible" EXTENT="2 letters"> Experiments and Rea&s;ons, which &s;eem to me very much to encounter the Sup|po&s;ition.</P>
<P>I &s;hall begin with that whereunto I am &s;ure they are furni&s;hed with an An|&s;wer, but &s;uch an An&s;wer as will give me the opportunity of a Reply, which po&s;&s;ibly may be of more moment, than if the Experiment it &s;elf were without an An&s;wer.</P>
<P>Take a pair of Scales, the one Di&s;h of 12
<PB N="71" REF="39">Inches of diameter, the other of 3 Inches diameter, yet of that thickne&s;s, that it may be ju&s;t of the &s;ame weight with the other, each di&s;h weighing for the pur|po&s;e three Pounds. The&s;e two Di&s;hes will yet exactly equiponderate, yet the one &s;u&s;tains a Column of Air of above twelve times the weight of the other, yea and according to the proportion a|bove computed, po&s;&s;ibly the greater Column impending upon the greater Di&s;h, may weigh above 4000l weight.</P>
<P>But there is a common An&s;wer &s;in|gularly fitted to this difficulty. For it is &s;aid, there is a Column of Air below each Di&s;h, that hath a Superficies com|men&s;urate to the lower Ba&s;e of each Di&s;h, which though it be but 3 or 2 or 1 foot, nay but an Inch above the Earth, bears up each Di&s;h as &s;trongly as the Column of Air of 7 miles high bears them down, and &s;o there is an <HI>aequipondi|um</HI> between the <HI>pondus deprimens</HI> upon the upper &s;ide of the Scale, and the <HI>pa|tientia &s;u&s;tinens</HI> of the lower &s;ide, and the Pillar of a Foot of length, between the Earth and the greater Scale, is of a
<PB N="72" REF="40">Foot diameter, and &s;u&s;tains it as forcibly as the <HI>pondus deprimens</HI> of a Foot diame|ter depre&s;&s;eth it, and &s;o it is &s;upported by an equal force impelling it upward, as it is depre&s;&s;ed by the weight of Air incumbent upon it. And the ca&s;e is the &s;ame with the le&s;&s;er Scale, and &s;o the greater Scale, though it hath a greater weight than the le&s;&s;er impendent upon it; &s;o it is recompen&s;ed with a more forcible power than the le&s;s hath to &s;u|&s;tain it, and &s;o there is an <HI>aequipondium.</HI></P>
<P>But although this &s;eems marvellous, that the <HI>potentia</HI> of a Pillar of Air from the Earth to the Ba&s;e of the Scale &s;hould counterpoi&s;e &s;o va&s;t a weight, as what is incumbent upon it, yet to &s;erve the turn, and to give a Solution by the weight and power of the Air to main|tain the cohe&s;ion of two poli&s;hed Mar|bles (<HI>de quo infra</HI>) this rea&s;on is given, that as there is a va&s;t weight of Atmo|&s;phere upon the Scale, &s;o there is the &s;ame Gravitation of Air round about it all, but what is ju&s;t under the Scale; and this impending Air round about the &s;ides of the Scale, as it is &s;o much, &s;o it
<PB N="73" REF="40">is &s;omewhat weightier than that which impends upon the Scale; for this reaches only to the Scale, and that reacheth &s;omewhat farther in length, even by &s;o much as the di&s;tance is be|tween the Earth and the Scale; and this doth &s;o gird and help in that &s;hort Co|lumn of Air &s;ubjacent to the Scale, that it is as firm a Pede&s;tal or <HI>potentia</HI> to &s;u|&s;tain the Scale, and to pre&s;s it up by the auxiliary Columns of Air, that &s;upply and &s;upport it, as the impending Co|lumn is to depre&s;s it, and &s;o between both there is an <HI>aequipondium.</HI> So that in all ca&s;es, as well in Air as Water, the &s;ubjected Column &s;u&s;taining and im|pelling upwards, and the <HI>potentia</HI> there|of is of equal force to the <HI>pondus</HI> of the &s;uperior Column, depre&s;&s;ing the upper Superficies of the intermediate Body.</P>
<P>And the &s;ame they &s;uppo&s;e in Water, the in&s;tances whereof is the Valve, and &s;ome other in&s;tances; but of the&s;e in the former Chapter.</P>
<P>And now upon this Suppo&s;ition of the <HI>potentia &s;u&s;tinens</HI> of the recoiling Pillar, as I may call it, &s;u&s;taining and im|pelling
<PB N="74" REF="41">up the lower Super&s;icies of the body, they have rai&s;ed mo&s;t marvellous Paradoxes and Con&s;equences, namely, that if a Mil&s;tone were by &s;ome art &s;u&s;|pended in the Air, if it were po&s;&s;ible that the Pillar of Air incumbent upon it were either wholly taken away, or de|prived of all Gravitation, this Mil&s;tone would be &s;u&s;tained by the &s;ubjected Co|lumn of Air, and po&s;&s;ibly carried up much higher, yea, and if a long Co|lumn of Bra&s;s were let down deep e|nough into the Ocean, they a&s;&s;ign a depth, at which the Column of Bra&s;s would &s;ink no lower, but be &s;u&s;tained by that marvellous <HI>potentia</HI> of the recoil|ing or &s;ubjected Column of Water: things that I confe&s;s are wittily dedu|ced, and con&s;equential enough upon their <HI>po&s;tulata</HI> admitted, but &s;uch as are warily enough propounded, becau&s;e impo&s;&s;ible to be tried.</P>
<P>But in an&s;wer to this Que&s;tion like|wi&s;e, I &s;ay this will be found untrue, and therefore although the Con&s;equences are Logically enough inferred upon &s;uch premi&s;es; yet the thing proving
<PB N="75" REF="41">fal&s;e in the event, the Premi&s;es, Princi|ples, and <HI>Po&s;tulat a</HI> them&s;elves mu&s;t needs be fictitious and vain.</P>
<P>Suppo&s;e therefore two &s;mall Cylin|ders of Bra&s;s, each of 41 weight, but the one of two Inches diameter, the other of one Inch diameter, and therefore about double the length of the other, were weighed in a ve&s;&s;el of Water by a pair of Scales, with the Superficies of each ju&s;t even with the Superficies of the Water in the ve&s;&s;el, they will each lo&s;e a ju&s;t equal portion of their weight by the thickne&s;s of the <HI>medium,</HI> and will &s;till hold their <HI>aequipondium,</HI> yet the imagina|ry column of Air impending upon the two Inches Cylinder above treble the weight to that impending upon the one Inch diameter, and here is no recoiling Column of Air to &s;u&s;tain them.</P>
<P>But I ea&s;ily fore&s;ee the An&s;wer to this In&s;tance, and therefore I gave it to let in what I have to &s;ay; for it will be &s;aid, that the Gravitation of the Air upon the re&s;idue of the Water, gives a greater concrete weight to the Water, by &s;o much as the Column of Air, commen|&s;urate
<PB N="76" REF="42">to the Superficies of the Water, adds to it, and &s;o both Air and Water make one common pre&s;&s;ure, and con&s;e|quently the recoiling or &s;u&s;taining Co|lumn of Water, hath as great a <HI>potentia &s;ustinens</HI> as the weight of both put toge|ther can contribute. But to avoid this <HI>Effugium,</HI> &s;ir&s;t I took two Bra&s;s Cylin|ders, weighing each four pound, but one of double the others diameter, I took then two Laton-Tubes of 6 Inches dia|meter, and about two foot in length, clo&s;ed at both ends, only in the centre of the clo&s;e Cover of the one I cau&s;ed a hole to be made, commen&s;urate to the Superficies of the Cylinder of Bra&s;s of 2 inches diam. &amp; a like hole in the other, commen&s;urate to the cylinder of Bra&s;s, of 1 Inch diameter, &s;o that they might ju&s;t play upon them without any con&s;idera|ble di&s;tance between the weights, and the concavity of the holes. I then filled the ve&s;&s;els brim full of water, &amp; weighed the Cylinders with their Superficies ju&s;t equal with the Water and Cover. Here could be no Gravitation of the Air upon any part of the Water, but only upon
<PB N="77" REF="42">the Weights, &s;o that the Column of Air, pre&s;&s;ing upon the greater Weight, being, as is &s;uppo&s;ed, above treble to what pre&s;&s;eth upon the le&s;s, mu&s;t needs drive it down, becau&s;e the recoyling Pillar of Water, could not counter|vail &s;uch a di&s;parity of <HI>pondus</HI> of Air.</P>
<P>And yet I found not above one Grain odds in their Weights, the broader weighing about a thin Groat more than the narrower.</P>
<P>But becau&s;e I would have no eva&s;i|on, by &s;uppo&s;ing that that &s;mall di|&s;tance between the Weights and the Hole, might give &s;ome more help and &s;trength to the &s;u&s;taining Pillar of Wa|ter by letting in &s;ome Air to lean upon the Water, thereby to enable it to keep the <HI>Equipondium.</HI> I took a very flat peece of Lead, with a hole in the Cen|tre, no bigger than would let through Freely that &s;mall Packthrid that &s;u&s;pen|ded the Weight, and letting the Thrid through the hole, and pre&s;&s;ing the Lead &s;o exactly clo&s;e, that no Air can pa&s;s to pre&s;s upon the Water and Weight, but ju&s;t that little pa&s;&s;age for
<PB N="78" REF="43">the Thrid which impended al&s;o in the very middle of the Weight, and there|by covering the Orifice, fitted to the one Inch weight; yet the <HI>Equipondium</HI> between both, continued exactly the &s;ame, as when both holes were left open, one of two Inches, the other of one Inch Diameter, at both times, the Ve&s;&s;els being perfectly full of Water.</P>
<P>And yet according to the &s;uppo&s;ition, the &s;uppo&s;ed Weight of the Pillar of Atmo&s;phere impendent upon the two Inch Weight, could not be &s;o little as 200 pound, and the weight of Air, pre&s;&s;ing upon the Centre of the le&s;&s;er Weight, and no where el&s;e, being not a quarter of an Inch Diameter, could not in proportion, weigh the 100^t^h part of 200 pound, according to the &s;uppo|&s;ition of this new Philo&s;ophy: And all this while the entire Superficies of the Water, di&s;charged of all manner of Gravitation of &s;uperior Air, by the clo&s;e cover that every where covered its Super&s;icies.</P>
<P>I do not under&s;tand what eva&s;ion can be made, unle&s;s they will &s;uppo&s;e that
<PB N="79" REF="43">the little hole for the Thrid, might by a &s;trange Contagion, infect the entire Body of Water, with a new Gravitati|on, which neverthele&s;s is &s;o impo&s;&s;ible, that it de&s;erves no other an&s;wer than what our common &s;en&s;e allows; for this little pertu&s;e, letting in that little Column of Ayr of a quarter of an Inch Diameter, impends not upon the Water, but is wholly received by the Bra&s;s Weights, upon who&s;e Centres it leans.</P>
<P>So that the imaginary repercu&s;&s;ive Column bearing up the Body into an Equilibrium, with the impendent Co|lumn of Air (admitting the Air &s;hould have &s;uch a Gravitation downward) mu&s;t needs be a fiction upon a fiction, and therefore upon the whole matter laid together, both are fictions, and nei|ther true.</P>
<P N="2">2. But yet farther, if &s;uch a pre&s;&s;ure upward of the inferior, or (as I have called it) the recoyling Column of Air &s;hould be admitted, it doth wholly de|&s;troy the &s;uppo&s;ition of Gravitation of the &s;uperior Column of Air, becau&s;e
<PB N="80" REF="44">in truth it renders the &s;uperior and in|ferior Columns of Air in a perfect <HI>aequi|librium,</HI> every lower portion of Air checking and counterpre&s;&s;ing the &s;u|perior, with the &s;ame &s;trength or <HI>poten|tia &s;u&s;tinens,</HI> that the &s;uperior portion chargeth the inferior with a <HI>pondus de|primens.</HI></P>
<P>(<HI>Fig.</HI> 5.) For &s;uppo&s;e in the 5^t^h Fi|gure <HI>A B</HI> were a Cylinder or Column of Air, reaching from <HI>A</HI> the Super&s;icies of the Atmo&s;phere, to <HI>B</HI> the Superficies of the Earth, and of 12 Inches diameter. If the portion <HI>B E F</HI> pre&s;s with an equal <HI>potentia</HI> upward to the portion <HI>A E F,</HI> pre&s;&s;ing with an equal weight down|ward; then the&s;e two portions of Air mu&s;t be at re&s;t, and <HI>in aequilibrio,</HI> and &s;o far every divi&s;ible part of every other portion of the entire Column. And if the &s;uperior and inferior parts of the Air be by this means <HI>in aequilibrio,</HI> there can be no more Gravitation downward than upward; for all motion mu&s;t ari&s;e from a di&s;parity of weight and weight, or power and power, or power and weight. And therefore it is that al|though
<PB N="81" REF="44"> one Scale be charged with a hundred pounds weight, and the other Scale be charged with as much, the Scales will be at re&s;t, becau&s;e <HI>in aequili|brio;</HI> and by the advantage though but of a Grain of weight, added to one Scale, they will be put into motion, but not 'till then.</P>
<P>But then it will be required to make out that, upon the Suppo&s;ition, that in our fir&s;t In&s;tance the greater Scale is kept <HI>in aequilibrio</HI> by the <HI>pondus</HI> of the &s;uperior, and the <HI>potentia</HI> of the inferior Air; that there will be the &s;ame <HI>aequi|librium</HI> between the <HI>pondus A E F,</HI> and the <HI>potentia E F B,</HI> upon or in every ima|ginary Superficies of the Column of the Atmo&s;phere; as <HI>E F C D,</HI> or any other imaginary &s;uperficient, interja|cent between the top of the Atmo|&s;phere <HI>A,</HI> and the Superficies of the Earth at <HI>B.</HI></P>
<P>And &s;urely there need not be much pains taken to prove this: for it is not the interpo&s;ition of the Scale that makes the <HI>aequilibrium,</HI> but it is the coun|terpre&s;&s;ure of the &s;uperior and inferior
<PB N="82" REF="45">part of the aerial Cylinder, which mu&s;t needs be as effectual, and of the &s;ame kind and &s;trength, if that Scale were removed out of the way; for though the interpo&s;ition of the Scale hinder the contiguity of the upper and lower Cy|linder, yet it contributes nothing to the Gravitation of the one, or pre&s;&s;ure upward of the other.</P>
<P>Upon all which large digre&s;&s;ion, it &s;eems to me that their very an&s;wer given, that the equal Gravitation of each Scale, the greater and the le&s;&s;er, is by the equal pre&s;&s;ure, <HI>viz.</HI> by rea&s;on the greater Scale as it is pre&s;&s;ed by a greater aerial Cylinder, is al&s;o &s;upported by a rever&s;ed or recoiling Cylinder of Air of equal &s;u&s;taining force, though not of equal length with the &s;uperior, de|&s;troys totally their whole Suppo&s;ition of the Gravitation of the Air, and ren|ders their contrivance of the inve&s;tiga|tion of the weight of the Atmo&s;phere, by the <HI>aequipondium</HI> thereof, to a Cylin|der of 29 Inches of Mercury, utterly ineffectual.</P>
<P>And this it &s;eems to me mu&s;t be ad|mitted,
<PB N="83" REF="45">namely that the inferior Cylin|der of Air recoiling and returning from the Earth, or any other &s;olid Ba&s;e, doth in truth &s;u&s;tain the impending <HI>pondus</HI> of the &s;ame Cylinder, and &s;o there is an <HI>aequipondium</HI> in any given or imagi|nary Superficies of Air between the <HI>pondus deprimens</HI> and the <HI>potentia &s;u&s;ti|nens,</HI> in the &s;ame perpendicular Pillar or Column: and &s;o the Air becomes not heavy in it &s;elf, but yet that it gravitates entirely upon the Ba&s;e, which is as it were the common <HI>hypomoclian</HI> that re|ceives the impre&s;&s;ion of the impendent Air, and remits the <HI>potentia</HI> upward in counterpoi&s;e to it.</P>
<P>But then they &s;ay, that where in that Pillar of Atmo&s;phere the Contiguity between the &s;uperior and inferior Co|lumn is interrupted by &s;ome interve|nient body: as in the fir&s;t in&s;tance, by the intervention of the Scale the <HI>aequi|pondium</HI> between the <HI>pondus deprimens,</HI> and the <HI>potentia &s;u&s;tinens</HI> of the aerial Pillar, is wrought by another means, namely the imaginary Pillars of Atmo|&s;phere circumjacent to that intercep|ting
<PB N="84" REF="46">body: as &s;uppo&s;e the three Co|lumns of Atmo&s;phere <HI>A M B N C O,</HI> and the Column <HI>B</HI> were cut off at <HI>D</HI> by any &s;olid body (&s;uppo&s;e the Scales, in the fir&s;t in&s;tance;) yet the two adjoin|ing Columns gravitate upon the infe|rior Pillar of Air (&s;uppo&s;e it tran&s;ver&s;e,) and &s;o give it as vigorous a repercu&s;&s;ion as if it were in the &s;ame perpendicular Column: as in the figure,</P>
<P>Suppo&s;e <HI>B H</HI> be a Column of Air, im|pending upon the cube <HI>H,</HI> of &s;ix Inches &s;quare; <HI>H</HI> to be (for in&s;tance) a cube of Bra&s;s, &s;ome way there &s;u&s;tained; <HI>E N</HI> be the &s;ubjected Column of the &s;ame ba&s;e, re&s;ting upon the Superficies of the Earth at N. Suppo&s;e al&s;o <HI>A D m,</HI> and <HI>C F o,</HI> be two lateral Columns of Air, pre&s;&s;ing <HI>g</HI> upon a lateral or tran&s;ver&s;al Pede&s;tal of Air <HI>G I K L,</HI> upon an imagi|nary Superficies, contiguous to the lower Ba&s;e of the cube H, namely <HI>G D F I;</HI> here the Cylinders <HI>H D</HI> and <HI>C F</HI> pre&s;s &s;o &s;trongly upon the entire tran&s;ver&s;al Ba&s;e <HI>G D E F G K L M N O,</HI> that the por|tion thereof <HI>E N</HI> is &s;o &s;trongly bound together, compre&s;&s;ed, and fortified by
<PB N="85" REF="46">the columns <HI>A D</HI> and <HI>C F,</HI> that it &s;u|&s;tains the cube <HI>H</HI> as forcibly as it would have &s;u&s;tained <HI>B H</HI> an entire Column of Air, and &s;o makes an <HI>aequipondium</HI> and &s;u&s;tentation of the cube <HI>H.</HI></P>
<P>(<HI>Fig. 6.</HI>) To examine the truth of this Suppo&s;ition, let us &s;uppo&s;e in this, <HI>A</HI> to be the ba&s;e of the cube <HI>B C D,</HI> and <HI>E</HI> to be the ba&s;es of four Pillars or Co|lumns of Air, contiguous to the four &s;ides of this cube, equal in Ba&s;e to it, and all the&s;e Ba&s;es, both of the cube <HI>A</HI> and of the four collateral Pillars of Air, to be upon the Superficies of the Earth. If <HI>A</HI> be removed higher, as to <HI>H</HI> in the former figure, the intermediate &s;pace between <HI>H</HI> (in the former figure) and the Superficies of the Earth, <HI>viz.</HI> the &s;pace <HI>H N,</HI> mu&s;t be furni&s;hed with Air; now the Air, that mu&s;t &s;upply that &s;pace, cannot be immediately thru&s;t in from the Pillar &s;uperior to the cube, <HI>viz. H B,</HI> becau&s;e the de&s;cent of that Pillar of Air is ob&s;tructed by the interpo&s;ition of the cube <HI>H,</HI> whereupon it is bot|tomed. Therefore of nece&s;&s;ity each of the collateral Pillars of Air, <HI>B C D E,</HI>
<PB N="86" REF="47">mu&s;t thru&s;t in an equal portion of their &s;tock of Air, to &s;upply the <HI>inter&s;titium</HI> of <HI>H n</HI> in the former figure; and then they will want &s;o much of their Pillar, as will make good what they have thus contributed to fill that &s;pace. And this they are to borrow from the Pillar <HI>H B,</HI> that lay perpendicular to the cube, which now at this Elevation is <HI>B H:</HI> for as the cube it gradually rai&s;eth from <HI>N</HI> towards <HI>H,</HI> the Pillar of Air incum|bent upon it mu&s;t be di&s;placed, and what is &s;o di&s;placed, mu&s;t be thru&s;t into the lateral Pillars <HI>B C D E,</HI> to &s;upply what they contribute to the relicted &s;pace <HI>H N:</HI> and &s;o in every Elevation higher of the cube <HI>H,</HI> &s;o much &s;pace as it leaves, mu&s;t be immediately thru&s;t in from the collateral Pillars adjacent to the Tube, and mu&s;t be made good in the &s;ame moment from the Air, thru&s;t out of the perpendicular Pillar <HI>B H,</HI> by the gradual Elevation of the cube to &s;upply the collateral Pillars. By this proce&s;s of one part of the Air into ano|ther, to accommodate the motion of its parts, it &s;eems evident, that there is not
<PB N="87" REF="47">that pre&s;&s;ure of one part of the Air upon another, nor of all upon the common Ba&s;e, that &s;hould be like &s;o many Wed|ges to keep every portion of Air ju&s;t in that place it hath; or by Gravitation of one part upon another, to keep all the parts &s;o tight one to another, as the <HI>Suppo&s;ition</HI> imports. For then certainly there could be no motion or tran&s;mi|gration of one part of the Air into ano|ther, as we &s;ee there is not only in the In&s;tance above given, but in a thou&s;and more. The mo&s;t forcible Winds could no more remove one portion of Air out of its place, then they could remove a Pyramid of <HI>Memphis,</HI> if this Sup|po&s;ition were true.</P>
<P>Therefore there &s;eems to be very lit|tle ground for the late Ma&s;ters of Expe|riments, to lay any weight of proof for their &s;uppo&s;ed Gravitation of the Air, upon the <HI>Torricellian</HI> Experiment; which, by what I have &s;aid, and &s;hall hereafter &s;ay more at large, depends upon a clear other Solution.</P>
<P>And thus far in general, touching the Gravitation of Air in Air, or upon
<PB N="88" REF="48">any other Bodies; wherein I have been the longer, becau&s;e I &s;hall perchance hereafter have recour&s;e to &s;ome of the things &s;aid in this Chapter.</P>
</DIV2>
<DIV2 N="5" TYPE="chapter">
<HEAD>CHAP. V.</HEAD>
<HEAD TYPE="sub"><HI>Concerning the Gravitation of heavier Fluids upon tho&s;e that are lighter.</HI></HEAD>
<P>THere be tho&s;e that contend, that there is no Body po&s;itively light, but only comparatively; and that the A&s;cen&s;ion of any Bodies is not from the intrin&s;ick nature or quality of the Bo|dies them&s;elves, but becau&s;e others that are more heavy than tho&s;e are, and more vigorous in their de&s;cent, do drive up tho&s;e that are le&s;s heavy, by taking their places, and &s;o force them to mount higher.</P>
<P>Whatever may be &s;aid in this re&s;pect, in relation to Air, yet &s;urely it holds true in other gro&s;&s;er Fluids, and &s;ome|times in &s;olid Bodies al&s;o: Oyl is truly heavy, and yet driven higher by Wa|ter,
<PB N="89" REF="48">which is ordinarily heavier than Oyl. And the &s;ame is true in relation to Water and Mercury, the latter dri|ving up the former though a heavy Body, becau&s;e not &s;o heavy as Mercury. As I have before &s;aid, there is a double Di&s;parity or <HI>aequipondium</HI> of heavy Bo|dies; one in relation to their intrin&s;ick of &s;pecifical weight, another in relation to the external or quantitative weight. Water is &s;pecifically heavier than Oyl, and Mercury than Water; whence it comes to pa&s;s, that a bulk of Mercury weighs more than a bulk of Water equal to the bulk of Mercury; one &s;quare Inch of Mercury, counterpoi&s;ing neer 14 &s;quare Inches of Water. But yet the bulk or quantity of Water may be &s;o much, or &s;o great, that it may overpoi&s;e the Mercury, two ounces of Water ne|ce&s;&s;arily being more, and weighing double to an ounce of Mercury, though &s;pecifically heavier than Water.</P>
<P>And therefore in the con&s;ideration of the gravitation of heavy Fluids upon lighter, we are to take the&s;e two parts into con&s;ideration. <HI>viz.</HI></P>
<PB N="90" REF="49">
<P N="1">1. The Gravitation of a Body, &s;pe|cifically heavier, upon or in a Body &s;pe|cifically lighter; as the Gravitation of Mercury upon Water, or Water upon Oyl or Air.</P>
<P N="2">2. The Gravitation of a Body &s;pe|cifically lighter, yet in quantity or ex|trin&s;ically heavier than the Fluid it pre&s;&s;eth; as two pound of Oyl upon a pound of Water, and the like.</P>
<P>As to the former of the&s;e, there &s;eem to be four ways, wherein the Gravitati|on or pre&s;&s;ure of a Fluid upon a Fluid, &s;pecifically lighter, &s;en&s;ibly is exerci&s;ed. <HI>viz.</HI> 1. By way of Penetration, 2. by way of perpendicular, or other de&s;cen|ding Depre&s;&s;ion, 3. by way of lateral Pre&s;&s;ure, 4. by way of Elevation of the lighter Body.</P>
<P>For the fir&s;t, if a cube of 12 Inches &s;quare be filled 9 Inches with Oyl, and the other three be filled up with Water; though for the pre&s;ent the Water gent|ly poured on will flote upon the Oyl, yet in a little time it will penetrate through it, and get under it, and the 9 Inches of Oyl will &s;wim upon it, pre&s;|&s;ing
<PB N="91" REF="49">its Superficies equally every where.</P>
<P>And &s;o if a <HI>lumen</HI> be at the bottom of the cube, the Water fir&s;t, and then the Oyl, will gravitate upon the Air, and pre&s;s through it.</P>
<P>But if the top of the cube be clo&s;ely covered, &s;o that Air cannot get in above the Water, the Oyl will not de&s;cend through the <HI>lumen,</HI> the rea&s;on whereof is hereafter explained.</P>
<P>For the &s;econd, it is very plain, that the heavier Fluid will in &s;ome In&s;tances pre&s;s upon all the lighter, by a depre&s;&s;ion where it can have way; &s;ometimes im|mediately, &s;ometimes mediately, <HI>viz.</HI> notwit&s;tanding the interpo&s;ition of an|other body. For in&s;tance,</P>
<P>If an empty Bottle or Gla&s;s-bubble be placed in a ve&s;&s;el of Water, at a &s;mall depth, the Air included in the Bottle or Bubble, being a Body lighter than Wa|ter, will mount up to the top, if it be not kept down: for a &s;mall pre&s;&s;ure of Water, though it pre&s;s upon the inclu|ded Air as much as it can, yet it cannot compre&s;s the Air &s;o much, as to drive into it a quantity of Water, that may
<PB N="92" REF="50">make the Bottle and included Water equal in weight, or more in weight than the like bulk of &s;imple Water; but if more Water be poured into the ve&s;&s;el, whereby a weight of Water incumbent upon the narrow mouth of the Bottle or Bubble, is &s;ufficient to compre&s;s the included Air, to &s;uch a contraction, as may admit Water enough to make the Bottle, with the admitted Water, to counterpoi&s;e more than a like quan|tity of &s;imple Water, the Bottle or Bub|ble will &s;ub&s;ide, and &s;ink to the bottom again; if the ve&s;&s;el be unladen con&s;ide|rably of its Water, whereby the Air included in the ve&s;&s;el being under a le&s;s pre&s;&s;ure, can expand it &s;elf to its natu|ral dimen&s;ion, and thereby thru&s;t out of the Bottle &s;o much of the included Wa|ter, as may render the Bottle, with the included Water, lighter than a like quantity or bulk of &s;imple Water, equal to the bulk of the Bottle, the Bottle will emerge again.</P>
<P>This is the Experiment mentioned by <HI>Shottus,</HI> in his <HI>Magia hydraulica, par|te 3, l. 5, problem. 3.</HI> and the excellent
<PB N="93" REF="50">Author of <HI>Hydro&s;tatical Paradoxes, pag.</HI> 16, 53, 153. and el&s;ewhere. The Ex|periment is certainly true, but the So|lution thereof, and the Conclu&s;ion de|duced from it, of the Gravitation of the upper parts of the Water upon the low|er, is as I think wholly mi&s;taken; for the rea&s;on of it is not from the imagi|nary Gravitation of Water upon Wa|ter, but of Water upon Air, which be|ing a lighter body than Water, and ca|pable of compre&s;&s;ion into a narrower compa&s;s, by the Gravitation of Water upon it, &s;u&s;tains that weight of the Wa|ter, and is compre&s;&s;ed by it, and under it: it is not an effect of Gravitation of Water upon Water, which is of equal intrin&s;ick or Specifical Gravity, but of Water upon Air, which is a lighter Fluid, and compre&s;&s;ible. Again, this Gravitation of heavier Fluids upon lighter, though not immediately conti|guous, is plain by this in&s;tance.</P>
<P>If a Cylindrical ve&s;&s;el of Water be of <HI>6</HI> Inches diameter, and there be a rundle of Wood &s;pecifically lighter than Water of five Inches &frac34; diameter
<PB N="94" REF="51">placed at the very bottom of it, the Water will drive it up to the Superfi|cies of it, becau&s;e it is a Body &s;pecifically lighter than the Water. But if there be a hole of five Inches diameter in the bot|tom of that ve&s;&s;el, and the Rundle be placed upon that hole, &s;o that it &s;ome-what overlaps the hole, &s;o that the Wa|ter cannot pa&s;s out of it, and then it be filled up with Water; the Rundle will gravitate upon that hole, and the in|cumbent Cylinder of Water, commen|&s;urate in Ba&s;e to that Rundle, &s;o hard and clo&s;e, that it requires a weight in a pair of Scales, neer commen&s;urate to the weight of the impending Cylinder of Water, to rai&s;e it from the bottom; and the rea&s;on is, becau&s;e the Rundle being the <HI>Operculnm</HI> of that hole, through which the Water &s;hould pa&s;s into the lighter Fluid, the Air, and &s;o is the impediment of the Waters pa&s;|&s;age, it gravitates upon it, becau&s;e it hath mediately a lighter Element upon which it gravitates, namely the Air. It is <HI>Stevinus</HI> his Experiment, in his <HI>pra|ctical Hydro&s;taticks,</HI> upon his 10. Pro|po&s;ition.</P>
<PB N="95" REF="51">
<P>And upon the &s;ame rea&s;on it is, that if a Gla&s;s-bottle filled with Sea-water, and &s;topped, be let down twenty fa|thoms into the Sea, it will not break, for it is filled with a Fluid of an equal weight, and &s;o the external Water doth not &s;en&s;ibly gravitate upon it, for it hath within a &s;ufficient power to re&s;i&s;t the external pre&s;&s;ure. But if it be full only of Air, and &s;topt, and let down as deep by a weight appended to it, (as it mu&s;t) it will be broken by the pre&s;&s;ure and weight of the Water immediately upon the inclu|ded Air, which is lighter than &s;o much Water, and &s;o it pre&s;&s;eth upon it, to drive it up, and cru&s;heth the gla&s;s into it.</P>
<P>And this I take to be one rea&s;on, though not the only rea&s;on of the Experiment of the Valve, and likewi&s;e of Oyl thru&s;ting up Water into a Tube, though of a &s;peci|fically heavier con&s;i&s;tence; and po&s;&s;ibly may contribute &s;omething to the in|&s;tance in the fourth Chapter, whereby a Syphon filled up with Mercury to the hight of the &s;horter leg, and immer&s;ed in Water, the Mercury in the &s;horter legg will &s;ub&s;ide a little, and a&s;cend in the lon|ger
<PB N="96" REF="52">leg, although the Mercury be a Body 14 times heavier than Water; for in the&s;e in&s;tances, though the immediate contiguity be of the heavier Body to the lighter, as Oyl to Water, and Water to Mercury, yet in as much as the Mer|cury in both leggs is in <HI>aequilibrio,</HI> and the Air is behind the Mercury in the longer legg of the Syphon, and behind the Water in the Tube, the Water in the one ca&s;e, and the Oyl in the orther, doth in truth gravitate upon that Air mediately and effectively, rather than upon the intermediate heavier. Fluid, e&s;pecially if the body of the Air be any whit lower than the Superficies of the Water.</P>
<P>And thus far touching the Gravita|tion or pre&s;&s;ure of a Fluid &s;pecifically heavier, upon a Fluid &s;pecifically lighter. I &s;hould now come to con&s;ider the pre&s;|&s;ure of a Fluid &s;pecifically lighter, yet with an exce&s;s of extrin&s;ick or quantita|tive weight upon a Fluid &s;pecifically heavier; as two pound of Water upon a pound of Mercury, or two pound of Oyl upon a pound of Water: but be|cau&s;e
<PB N="97" REF="52">this and &s;ome other con&s;iderati|ons, for the better clearing of the mat|ters contained in this Chapter, may oc|cur in the next, I &s;hall remit it thither.</P>
</DIV2>
<DIV2 N="6" TYPE="chapter">
<HEAD>CHAP. VI.</HEAD>
<HEAD TYPE="sub"><HI>Concerning the Pre&s;sure or Gravitation of lighter Fluids, upon tho&s;e that are &s;pe|cifically heavier.</HI></HEAD>
<P>IT is certain, that every Body, whi|the fluid, or &s;olid, incumbent upon another, though that Other be a thou|&s;and times intrin&s;ically and al&s;o extrin|&s;ically heavier than the incumbent Bo|dy doth gravitate and pre&s;s upon it.</P>
<P>And therefore if we &s;hould &s;uppo&s;e the Air to have a weight, but a thou|&s;and times le&s;s than the like portion of Water, a portion of one &s;quare foot of Air incumbent upon the Ocean, would have &s;ome pre&s;&s;ure upon it: &s;ome|what like the Problem that pa&s;&s;ed in the Affirmative among Fre&s;h-men in the Univer&s;ity, <HI>That if a Hor&s;e had as much as he could carry, the addition of the weight of the thou&s;andth part of a Fea|ther
<PB N="98" REF="53">would break his back.</HI></P>
<P>But this is not the pre&s;&s;ure or Gravi|tation I am &s;peaking of, but &s;uch a Gra|vitation or pre&s;&s;ure, as would put the &s;ubjected heavier Fluid into a &s;en&s;ible motion, or change of place or &s;ituation.</P>
<P>In a pair of artificial Scales, a pound of Feathers or Water, will equiponde|rate a pound of Gold or Mercury, and 2 pound of Feathers will preponderate a pound of Gold or Mercury, not with&s;tan|ding the great di&s;parity of their intrin|&s;ick weight.</P>
<P>And &s;o in a Ballance that &s;eems more natural, if a Syphon of half an Inch dia|meter, with one legg of &s;ix Inches long, and the other of thirty four Inches long, or more, be filled with Mercury to the height of the &s;horter legg, and then &s;topping the Orifice of the &s;horter legg with the finger, fill the longer legg with water, and then opening the Orifice of the &s;horter legg, the Water in the longer legg, though &s;pecifically lighter than the Mercury, will drive out the Mercury out of the Syphon, be|cau&s;e the extrin&s;ick or quantitative
<PB N="99" REF="53">weight of &s;o much Water exceeds the extrin&s;ick or quantitative weight of the &s;ubjacent Mercury.</P>
<P>If a cubick ve&s;&s;el be filled &s;ix Inches high with Water, and a Gla&s;s-pipe open at both ends be immer&s;ed at one end in the Water, and then &s;uperinfu&s;e gently (to avoid di&s;turbance) &s;o much Oyl as will fill it up ten Inches, <HI>viz.</HI> four In|ches of Oyl, and &s;ix of Water, the Pipe will be filled with Water neer to the le|vel of the Superficies of the Oyl, but not quite level to the Superficies of the Oyl, it will want &s;o much, as the like quantity of Water in the Pipe, is heavier than the like quantity of Oyl.</P>
<P>But if a Pipe filled with Oyl, and the upper end &s;topt with a finger, whereby the Oyl remains &s;u&s;pended in the Tube, or Pipe, and then the open end be im|mer&s;ed in the Water, the Oyl, while it obtains a Superficies in the Pipe con&s;i|derably higher than the Water in the ve&s;&s;el, will &s;ub&s;ide 'till it come to &s;uch an Elevation above the Superficies of the Water, as is proportionable to the degree of &s;pecifical Lightne&s;s that it
<PB N="100" REF="54">obtains more than the like quantity of Water. And 'till then it &s;ub&s;ides into the Water, becau&s;e it hath a greater proportion of accidental weight by its &s;o great Elevation above the Super&s;i|cies of the Water: for the Elevation of one fluid body above another, gives the greater &s;trength and &s;wifter motion to its de&s;cent: whereby though a ligh|ter body, it conquers the re&s;i&s;tance of the Water of a lower Superficies.</P>
<P>Which is the rea&s;on, why a Tube of Water, four foot high, ca&s;ts out more Water in the &s;ame portion of time, through the &s;ame <HI>lumen,</HI> than a ve&s;&s;el of the &s;ame diameter, and but two foot high, as I &s;hall hereafter more at large ob&s;erve.</P>
<P>And this is the rea&s;on, why if a &s;mall Gla&s;s-Tube of &s;ix Inches long, be filled with Water, and the upper end being &s;topped with the finger, whereby the Water is &s;u&s;pended in the Pipe, and then the lower end being immer&s;ed in a ve&s;&s;el of Water &s;ix foot deep, and then the upper end un&s;topped, the whole Water in the Pipe will empty it &s;elf,
<PB N="101" REF="54">'till it attain a Superficies equal with the Water in the ve&s;&s;el, and will not be kept &s;u&s;pended in the Pipe by the re&s;i&s;tance of the Water in the ve&s;&s;el, becau&s;e if it obtain never &s;o little more height in the Pipe than in the ve&s;&s;el, it hath a grea|ter force to pre&s;s downward, than the Water in the ve&s;&s;el hath &s;trength to re|&s;i&s;t it.</P>
<P>If a Tube &s;topt at one end be filled with Mercury, and inverted in the open Air, the Air will a&s;cend and terebrate through the Mercury as fa&s;t as that de|&s;cends; &s;o there is a kind of pre&s;&s;ure of the Air <HI>a&s;cendendo</HI> upon the Mercury, and thereby both the Air and Mercury obtain their &s;everal natural motions, this <HI>de&s;cendendo,</HI> and that <HI>a&s;cendendo,</HI> whereby Vacuity is prevented, and the continuity of the parts of the Univer&s;e pre&s;erved.</P>
<P>But if the Tube be very &s;mall, &s;o that the Air cannot make its way through the lower orifice, to gratifie the Mercu|ry with a de&s;cent, by that means the Mercury will remain &s;u&s;pended in the &s;mall Tube, and will not de&s;cend. The
<PB N="102" REF="55">like will happen, if &s;uch a &s;mall Tube be inverted into Water, the &s;mallne&s;s of the orifice not admitting the a&s;cent of the Water to &s;upply the &s;pace derelicted by a de&s;cent of the Mercury, the Mer|cury by force of the Catholick law of Nature will remain &s;u&s;pended, and its natural de&s;cent will be thereby &s;uper|&s;eded.</P>
<P>So that the pre&s;&s;ure or Gravitation of a lighter Body upon a more gro&s;s and weighty, will be occa&s;ioned, 1. Either by the Exce&s;s of the quantity and ex|trin&s;ick weight of the Fluid &s;pecifically lighter, or 2. by the advantage of its Po|&s;ition or Elevation above the Superfi|cies of the gro&s;&s;er Fluid, or 3. by the interpo&s;ition of that common law of Nature, <HI>ut evitetur vacuum.</HI></P>
<P>I &s;hall conclude the&s;e general Ob&s;er|vations, touching the Gravitation of Fluids, with that of the Valve, de&s;cri|bed by the Excellent Author of <HI>Hydro&s;ta|tical Paradoxes, cap. ultimo,</HI> which was certainly a mo&s;t ingenuous Experi|ment, though I am not at all &s;atisfied with the Solution he gives of it, nor the
<PB N="103" REF="55">Con&s;equences deduced by him from it, touching the Gravitation of Water upon Water, (I mean &s;en&s;ible Gravita|tion) of the &s;uperior parts upon the in|ferior parts of the Water in free water.</P>
<P>And I am as much di&s;&s;atisfied with that ob&s;cure Solution that is given thereof by the Learned Author of the <HI>Enchiridion Metaphy&s;icum.</HI></P>
<P>And becau&s;e in this one Experiment duly ob&s;erved and improved, many of the mo&s;t ab&s;tru&s;e Conclu&s;ions of Hy|dro&s;taticks may be cleared even to &s;en&s;e, I &s;hall di&s;tinctly examine it, and the <HI>phae|nomena</HI> appearing in it.</P>
<P>The In&s;trument is thus made, accor|ding to that form which I made u&s;e of.</P>
<P>I took a hollow Tube of Laton, clo&s;e|ly &s;odered at the Sides and joynts, of 39 Inches long, two Inches &frac12; in the dia|meter from the top to the bottom, with a Bra&s;s Valve at the end of it &s;odered to it, and a bra&s;s Sucker or Cover of the &s;ame fa&s;hion with tho&s;e u&s;ed in Pumps, only in Pumps the Cover or Sucker hath its head upward, in this In&s;tru|ment the head is downward, whereby
<PB N="104" REF="56">it being inverted it falls out about an Inch below the Valve, but cannot fall out more, becau&s;e &s;tayed by the Frame of the Valve.</P>
<P><HI>Fig.</HI> 7. This Sucker exactly covers the mouth of the Valve, that no water can come in, when the Sucker is clo&s;ely &s;trained up, by a &s;tring fa&s;tned to it in the inward pin of it, and &s;o conveyed up through the Tubes. The Sucker thus fa&s;tned to the Valve or Box, and the Box &s;oder'd clo&s;e to the Tube, and the &s;tring conveyed up through the Tube to the open end of it, the Engin is formed according to the Figure in the Margin, repre&s;enting <HI>A</HI> the Tube, <HI>B</HI> the String, <HI>C</HI> the brazen Box of the Valve &s;oder'd to the Tube, <HI>D</HI> the Sucker or Cover of the Valve let down as low as it will go, with a Hook to hold any weight appended to it; which Sucker being &s;trained up with the &s;tring, clo&s;e|ly &s;tops the lower orifice of the Tube, and Box of the Valve.</P>
<P>The Valve thus prepared, I &s;trictly weighed the whole Valve, Tube, Sucker, and Thrid, with the wooden
<PB N="105" REF="56">Nut upon which to roll the &s;tring, which weighed in all three pounds, two ounces and a half, or 50 ounces and a half.</P>
<P>The Sucker (for &s;o I &s;hall call the name of the Valve) weighed &s;even oun|ces and one half: and I was curious in weighing the&s;e things, becau&s;e the great u&s;e of my Experiments con&s;i&s;ted in the compari&s;on of weights of the In&s;truments them&s;elves, and the Water.</P>
<P>I took then a great gla&s;s Tube, of a|bout five Inches diameter, and about two foot and a half long, and filled it with Water; though I u&s;ed al&s;o a Leaden ve&s;&s;el of &s;ix Inches diameter, and four foot long, for the immer&s;ion of my Valve, which though it were deeper, yet the Gla&s;s ve&s;&s;el was more ac|commodate to my u&s;e, and &s;erved as well, and therefore I u&s;ed it, and there|upon made tho&s;e &s;everal Trials.</P>
<P>(<HI>Fig.</HI> 8.) 1. The Tube let into the Water, with the Valve open, would freely &s;ub&s;ide to the bottom of the Wa|ter, be it never &s;o deep, the water get|ting up into the cavity of the Tube: for
<PB N="106" REF="57">the <HI>moles</HI> of the Tube in that in&s;tance, is no more than the length and thickne&s;s of the Laton, the Bra&s;s Valve and Sucker; but the weight thereof being more than &s;uch a &s;ingle <HI>moles</HI> of water, it mu&s;t nece&s;&s;arily &s;ub&s;ide to the bottom of the water.</P>
<P N="2">2. The Valve being drawn up, and &s;u&s;tained by the Thrid wound about the wooden Nut at the top of the Valve, whereby no water could come into the Tube, and then left freely to &s;ub&s;ide in the water, would &s;ub&s;ide to a depth of one and twenty Inches, and &s;o &s;wim erect in that depth of water, one and twenty Inches being immer&s;ed in the water, and eighteen Inches of the Tube being in the open Air, above the Su|perficies of the water.</P>
<P>And the rea&s;on is, becau&s;e though the Laton and Bra&s;s be &s;pecifically hea|vier than Water, and therefore will &s;ink, as in the la&s;t In&s;tance; yet becau&s;e now the Tube &s;its upon the water, as one entire Cylinder, and a Cylinder of Laton thirty nine Inches long, and two Inches &frac12; broad filled with Air only, is
<PB N="107" REF="57">not heavier than a Cylinder of Water of one and twenty Inches long, and two Inches &frac12; diameter, but do equiponde|rate; therefore the Tube &s;inks no lower than one and twenty Inches to make an <HI>aequipondium</HI> between it &s;elf and the like bulk of Water.</P>
<P N="3">3. I therefore with all the exact|ne&s;s I could, mea&s;ured the weight of the Water commen&s;urate to a Cylin|der of two Inches &frac12; diameter, and one and twenty Inches long, (the quantity of the Tube &s;wimming in the Water.)</P>
<P>Fir&s;t therefore filling my Gla&s;s Tube very full of Water, I immer&s;ed the Valve open into one and twenty Inches deep; then at that depth lifting up the Sucker, and inclo&s;ing the one and twenty Inches of Water thus impri|&s;oned in the Tube, and &s;o taking it out clo&s;ed; and then when out of the Gla&s;s Tube &s;etting it to run into a ve&s;&s;el weighed before, I find the weight of the included Water weighed fourty and &s;even Ounces and half, or three pound wanting half an Ounce, which is about three Ounces le&s;s than the weight of
<PB N="108" REF="58">the whole In&s;trument. And this abate|ment it hath for the thickne&s;s of the Tube and Valve, becau&s;e the water that is pre&s;&s;ed upon by the Tube and Valve, and &s;o rai&s;ed out of its place, is pre&s;&s;ed up by the convex or out&s;ide of the Tube and Valve, and commen&s;urate to it.</P>
<P>Therefore again &s;training up the &s;tring of the Valve, whereby no water could get in, and filling my Gla&s;s Tube of re&s;tagnant water to the very brim or brink of the Gla&s;s, and then I immer|&s;ed my Tube into the water to one and twenty Inches depth; the Valve &s;trai|ned up by the &s;tring, and pre&s;erved the water that was impelled up by the im|mer&s;ion, and thrown over: and this I likewi&s;e exactly weighed, and found to weigh near upon the point of fifty one Ounces &frac12;, or three pound three Ounces and half, which is about an Ounce more than the weight of the Engine; which di&s;parity might happen for want of ex|actne&s;s. But the &s;umme of it is, there is no con&s;iderable difference between the weight of the whole Engine, and the weight of &s;o much Water, as will
<PB N="109" REF="58">countervail in quantity to &s;o much of the Engine or mingled Cylinder of 21 Inches thereof immer&s;ed in water.</P>
<P>Which gives us a plain account, why and how much a Body lighter than the like quantity of water, will &s;it a|bove water, and why, and how it comes to pa&s;s, that &s;ome Ships draw more water than others, and how much bur|then they will bear, before they will &s;ink, <HI>viz.</HI> if the Ship or Barge with all its Cavities and Lading, be not heavier than &s;uch a &s;olid bulk of water, as equals the whole <HI>Moles</HI> and Cavity of the Ship or Barge, the Barge will live, though it draw water neer to the very top of the &s;ides of the ve&s;&s;el. And if the Ship or ve&s;&s;el be lighter than &s;uch a <HI>moles</HI> of water as equals the whole con|tinent of the Ship or Barge, &s;o much of the Ship or Barge will emerge above the water. For in the in&s;tance in hand, in as much as 21 Inches of immer&s;ion of the Tube, was the product of its whole weight of three pound, two Ounces and half; and tho&s;e one and twenty Inches thus immer&s;ed, were
<PB N="110" REF="59">equal in weight to a bulk of Water, commen&s;urate to that Cylinder of 21 Inches immer&s;ed, the re&s;t of the Tube <HI>viz.</HI> 18 Inches, did flote erect upon the Water; for if it &s;hould have &s;ub&s;ided, the <HI>moles</HI> of Water lifted up out of its place would have exceeded the weight of the whole Valve, <HI>viz.</HI> three pound, two Ounces, and half, which by the rules and Laws of <HI>Hydro&s;taticks</HI> it may not do,</P>
<P N="4">4. If the Sucker be drawn up, and then immer&s;ed &s;o low, that the portion of Water impelled up by the Tube, do exceed the weight of the Sucker, <HI>viz.</HI> 7 ounces and half, the Sucker will be &s;u&s;tained by the pre&s;&s;ure of the Water upon it: as &s;uppo&s;e in the 8^t^h Figure it were pre&s;&s;ed even to <HI>L M,</HI> or <HI>N O,</HI> which is nine Inches below the Superficies of the Water. And the rea&s;on is, becau&s;e the Sucker is now the moveable Ba&s;is of the included Column of Air, which is a light Body, and &s;o gravitates no|thing upon the Water; and the Sucker being as it were the Ba&s;is of that Co|lumn, and moveable, weighs but &s;even
<PB N="111" REF="59">Ounces and half, and the Tube &s;ub&s;iding as low as <HI>L M</HI> or <HI>N O,</HI> pre&s;&s;eth up a portion of Water of double that weight, and this portion of Water bears again&s;t the Ba&s;e or Sucker more forcibly and powerfully than the Sucker can bear again&s;t it.</P>
<P N="5">5. But if the weight of a <HI>moles</HI> of Water, commen&s;urate to &s;o much of the Tube as is immer&s;ed in the Water, be le&s;s than the weight of the Sucker, the Sucker by its own weight will &s;ub|&s;ide, notwith&s;tanding its immer&s;ion in|to Water.</P>
<P>By iterated Trials I found, that if I kept up the Sucker by the Thrid, and immer&s;ed it to ten Inches, or more, and let go the &s;tring, whereby the Sucker, though now at liberty, would yet not &s;ub&s;ide, but remain &s;u&s;pended by the pre&s;&s;ure of the Water upon it; yet if I gently rai&s;ed it up, 'till it came only to an immer&s;ion of four Inches and half, the Sucker would &s;ub&s;ide; wherefore clo&s;ing in the included Water at that depth, by lifting up the Thrid, and &s;o clo&s;ing the Sucker, I weighed that in|clo&s;ed
<PB N="112" REF="60">Water, and found it ju&s;t weighed as much as the Sucker, <HI>viz.</HI> &s;even Oun|ces and half, and there could be no con|&s;iderable odds here by the thickne&s;s of the Tube, the immer&s;ed portion thereof being but&s;mall, and the &s;ides very thin.</P>
<P N="6">6. But becau&s;e I would pur&s;ue the proportion to the uttermo&s;t, I kept up the Sucker with the &s;tring, 'till the Tube came to the immer&s;ion of four Inches and half, and then &s;ub&s;ided; I then inclo&s;ed that four Inches and half of Water, and kept up the Sucker, and immer&s;ed the Tube with the inclo&s;ed four Inches and half of Water, and gent|ly rai&s;ing it up, it &s;ub&s;ided at nine Inches immer&s;ion.</P>
<P>And the rea&s;on is the &s;ame as before, for the included cavity of nine Inches, had in it four Inches and half of Air, which weighed nothing, and four In|ches and half of Water, which as before is &s;hewn, weighs &s;even Ounces and half, and the weight of the Valve which weighs al&s;o &s;even Ounces and half, the whole weight of the included Air, Wa|ter, and Valve, weighing only fifteen
<PB N="113" REF="60">Ounces, and a Column of Water of nine Inches high, and two Inches and half broad, equal to the cavity of the immer|&s;ed nine Inches of the Tube, would have been of the &s;ame weight with the four Inches and half of included Water; and the Sucker, who&s;e weight is now to make good the uppermo&s;t four Inches and half of Airy &s;pace, and &s;o there is and <HI>aequipondium</HI> between the included four Inches and half of included Water, together with the weight of the Sucker to a Cylinder of Water of nine Inches long, and two Inches and half broad, commen&s;urate to the like cavity of the Tube, and the like quantity of nine In|ches of Water, impelled out of its place by nine Inches of the Tube immer&s;ed below the Superficies of the Water.</P>
<P>And the &s;ame rule and proportion will hold upon the like quantity of more Water taken in, and a deeper immer&s;ion, allowing the &s;ame thing for that thickne&s;s of the &s;ides of the Tube, which upon a deep immer&s;ion is more con&s;iderable than upon an immer|&s;ion of four Inches and half.</P>
<PB N="114" REF="61">
<P N="7">7. And although I did not make an actual trial how much weight in an empty Tube, deeply immer&s;ed, would be &s;u&s;tained by the Sucker without &s;ub|&s;iding; yet by this proportion it is ea&s;ie to be calculated, <HI>viz.</HI> that the Tube be|ing kept empty, and immer&s;ed to any depth below four Inches and a half, the Sucker will &s;u&s;tain without &s;ub&s;iding &s;uch a weight, as is equal to a portion of Water commen&s;urate in bulk to &s;o much of that empty Cylinder in the Tube, as is depre&s;&s;ed below the Superfi|cies of the ve&s;&s;el of re&s;tagnant water.</P>
<P>So that if the empty Tube will &s;u&s;tain &s;even Ounces and half (the weight of the Sucker,) at four Inches and half im|mer&s;ion, it will &s;u&s;tain fifteen Ounces at nine Inches immer&s;ion, thirty Ounces at eighteen Inches immer&s;ion, &s;ixty Ounces at thirty &s;ix Inches of immer|&s;ion; for an empty Cylinder of thirty &s;ix Inches long and two Inches and half broad, will contain a Cylinder of Wa|ter of &s;ixty Ounces weight, allowing &s;omewhat as before, for the thickne&s;s of the &s;ides of the Tube.</P>
<PB N="115" REF="61">
<P N="8">8. In this it appears that the Water doth not gravitate upon the Water, but gravitates upon a Body lighter than it &s;elf, though this Gravitation be im|mediately upon a Body as heavy or hea|vier than it &s;elf. When there is nothing but Air in the Tube, the Sucker is the moveable Ba&s;is of that Air, and it gra|vitates immediately upon the Sucker, but mediately and remotely upon the Air above it, when there is a little co|lumn of Air in the top of the Tube, and below the Superficies of the Water, and under that a column of Water, and un|der that the Sucker. If the whole Con|crete be lighter than &s;o much Water, it gravitates upon the Sucker, Water, and Air, becau&s;e though the Bra&s;s be &s;pecifically heavier than Water, and the Water over it &s;pecifically of an equal weight with Water; yet the quantita|tive or extrin&s;ick weight of both is le&s;s than the weight of &s;o much Water as is equal to a Bulk or Cylinder of Water, entirely commen&s;urate to the quantity of the Air, Water, and Sucker, below the Superficies of the Water.</P>
<PB N="116" REF="62">
<P N="9">9. That when a Body lighter than &s;o much water is within the compa&s;s of the Superficies of the body of re&s;tagnant water, the water pre&s;&s;eth upon it up|ward, impelling it up, as here upon an immer&s;ion of the Valve laden with four Inches and half of water, and likewi&s;e with the weight of the Sucker, into nine Inches of water, an equal quantity of water to the <HI>moles</HI> of the immer&s;ed Tube, <HI>viz.</HI> nine Inches &s;u&s;tains the Sucker, notwith&s;tanding its own weight and the weight of four Inches and half of water incumbent upon it, becau&s;e tho&s;e two weigh but fifteen Ounces, and nine Inches of the exterior water weighs as much, and &s;o there is an <HI>aequi|pondium</HI> between the <HI>potentia &s;ustinens,</HI> and the <HI>pondus deprimens.</HI></P>
</DIV2>
<DIV2 N="7" TYPE="chapter">
<PB N="117" REF="62">
<HEAD>CHAP. VII.</HEAD>
<HEAD TYPE="sub"><HI>Concerning the Space derelicted by the de|&s;cent of the Mercury in the <HI>Torricellian</HI> Experiment, and what it is not, or what it is that fills it.</HI></HEAD>
<P>HAving gone through the two pre|mi&s;ed Con&s;iderations, prelimi|nary to this Inquiry, I now come to the third General, namely what it is that fills the &s;pace derelicted by the de&s;cen|ding Mercury in the Tube. And fir&s;t I &s;hall con&s;ider, whether it be a Space purely void of any Body. 2. If it hath &s;ome Body that fills that Space, I &s;hall con&s;ider what it is not that fills it. 3. I &s;hall con&s;ider what it is that mo&s;t pro|bably may be thought to fill it.</P>
<P>Fir&s;t therefore I &s;ay it is not Nothing, or a pure Vacuity, but it is &s;ome cor|poreal &s;ub&s;tance that &s;ucceeds in the head of the Tube, derelicted by the Mer|cury.</P>
<P>And here 1. I &s;hall not enter into
<PB N="118" REF="63">any large debate touching the po&s;&s;ibili|ty or impo&s;&s;ibility of inter&s;per&s;ed or coacervated vacuities in any parts of the Univer&s;e; neither 2. &s;hall I in&s;i&s;t upon tho&s;e ob&s;cure evidences of the in|exi&s;tence of a Body in that derelicted &s;pace; as namely the communication of Sounds, or the reception of Light, or tran&s;mi&s;&s;ion of Colours, or other vi|&s;ible <HI>&s;pecies</HI> in or from it. But 3. I &s;hall ground my Conclu&s;ion from tho&s;e more &s;en&s;ible and apparent <HI>Phaenomena</HI> which do evince it; namely, tho&s;e &s;en&s;ible plain Effects in that &s;eeming empty Space, which could never be produeed but by the contiguity and pre&s;ence of &s;ome corporeal &s;ub&s;tance, filling that &s;uppo&s;ed empty &s;pace.</P>
<P N="1">1. It is mo&s;t evident to any man's &s;en&s;e that will but try it, that if the Tube be open at both ends, and filled up with Mercury, and then one end &s;topped with the finger, and the other end inverted and immer&s;ed in the re&s;tagnant Mer|cury, whereby it de&s;cends from the top of the Tube, a &s;trong and &s;en&s;ible At|traction is wrought upon the pulp of
<PB N="119" REF="63">the upper finger that clo&s;eth it, which continues and grows more and more forcible, &s;en&s;ible, and evident, the farther the Mercury is removed from the upper end, and approaching to its u&s;ual &s;tation of 29 Inches.</P>
<P>This Attraction is impo&s;&s;ible to be without the contiguity of &s;ome Body to the pulp of the finger, which cannot be the Mercury it &s;elf, for That in a Tube of four Foot long is removed a|bove a Foot di&s;tant from the finger, by that time it comes to its &s;tation; yet all this while the &s;trong &s;uction upon the pulp of the finger continues.</P>
<P>And they that go about to tell us, that it is not Attraction or Suction by any power within the Tube, but by the pul&s;ion of the incumbent column of Air, need no other confutation than their own &s;en&s;e to a&s;&s;ure them the con|trary; for mo&s;t evidently the force that the finger feels is from within, and not from without: and this Solution by Pul&s;ion, is given only to gratifie that imaginary Suppo&s;ition that &s;ome have entertained of the Aery Column, where|of in due time.</P>
<PB N="120" REF="64">
<P N="2">2. The in&s;tance of <HI>Hanoratus Fabri</HI> in the 6^t^h of his <HI>Phy&s;ical Dialogue,</HI> (though not tryed by my&s;elf, yet a&s;&s;erted to be tryed by him) puts it out of que&s;tion. If at the upper end of the Tube there be fixed a folded Paper, which may be extended by any force, but otherwi&s;e contracting it &s;elf (in the manner of Paper-Lanthorns made by School-boys), this <HI>plicat a charta</HI> will by the &s;ub&s;iding of the Mercury be unfolded and exten|ded, which could not be, but by the contiguity of &s;ome Body unto it.</P>
<P N="3">3. The in&s;tance given by <HI>Linus,</HI> and improved by <HI>Fabri, ubi &s;upra,</HI> of an emp|ty Bladder clo&s;e tyed, and fa&s;tned to the upper end and the in&s;ide of the Tube, extended after the de&s;cent of the Mer|cury, and again contracting it &s;elf to its former dimen&s;ion by the inclination of the Tube, makes it plain, that this Extention is the effect of &s;ome included Body in that relicted &s;pace, which is not the bare gro&s;s body of the Mercury, which is removed a Foot or more below it, and in which there is not &s;o much as pretended to be any Magnetick qua|lity
<PB N="121" REF="64">in relation to the Bladder.</P>
<P>And they that tell us it is the Elatery of the Air included in the Bladder, that extends it by a natural expan&s;ion, tell us an invention fitted to &s;erve the Suppo|&s;ition of the prodigious natural Elatery of uncompre&s;s'd Air, whereof hereaf|ter.</P>
<P>It is true, that if this Bladder hath any little orifice, or hole open in it, the di&s;tention will not en&s;ue; but the rea|&s;on thereof is evident, (not upon their Suppo&s;ition of the impediment of the natural Elater of the Air included in the Bladder,) but becau&s;e in that ca&s;e the Attraction is made as well upon the in&s;ide of the Bladder through the orifice, as upon the out&s;ide, and &s;o the Bladder obtains the &s;ame con&s;i&s;tence as at fir&s;t; but where there is no orifice, the Attraction can only be but upon the out&s;ide of the Bladder, upon which there nece&s;&s;arily follows an Exten&s;ion of the Bladder, and a nece&s;&s;ary Con&s;e|quent thereof is a Dilatation and Ex|pan&s;ion of that little particle of Air in|cluded in it, to the uttermo&s;t dilatation
<PB N="122" REF="65">that that attractive force can give it, or produce in it, which is not by natural Ela&s;ticity, but by forcible Ten&s;ion.</P>
<P>Upon the&s;e and the like &s;en&s;ible and plain In&s;tances it &s;eems undeniable by any, that will not abandon his own &s;en&s;e, that it is not Nothing that is in that derelicted &s;pace, but it is &s;ome bo|dily &s;ub&s;tance; for otherwi&s;e it were impo&s;&s;ible that tho&s;e, and the like &s;en&s;ible effects could be produced: for regular|ly, all natural bodily effects are wrought by a contact of &s;ome Active body up|on the Patient.</P>
</DIV2>
<DIV2 N="8" TYPE="chapter">
<HEAD>CHAP. VIII.</HEAD>
<HEAD TYPE="sub"><HI>Concerning the Body &s;upplying the derelicted Space in the top of the Tube, and fir&s;t what it is not.</HI></HEAD>
<P>IN the former Chapter I have conclu|ded, that it is &s;ome corporeal Sub|&s;tance in the &s;pace derelicted by the Mercury in the top of the Tube, though not con&s;picuous to the &s;ight: and now
<PB N="123" REF="65">I &s;hall con&s;ider fir&s;t what it is not, and 2. what it &s;eems mo&s;t probably to be.</P>
<P>There are two general Opinions touching it: one that &s;uppo&s;eth it is &s;ome Body that comes <HI>de foris</HI> into that derelicted &s;pace; and tho&s;e again fall into &s;everal Opinions; &s;ome &s;uppo&s;e it to be the forreign Air that pervades ei|ther the Pores of the Gla&s;s, or the Mer|cury; others that it is <HI>Ather,</HI> or Ethe|real matter, or (which is a differing kind of Explication of the &s;ame thing) that it is <HI>des Cartes</HI> his <HI>materia &s;ubtilis,</HI> or his Third Element, the <HI>ramenta</HI> or filings of Atomical Bodies. The other gene|ral Opinion is, that it is a bodily &s;ub|&s;tance, not coming <HI>de foris,</HI> but ari&s;ing from the included Mercurial Body.</P>
<P>Now as to the former of the&s;e gene|ral Suppo&s;itions that it comes <HI>de foris,</HI> I &s;hall di&s;charge the que&s;tion from that Suppo&s;ition of <HI>des Cartes</HI> his <HI>materia &s;ubtilis,</HI> for there is no probable evidence of any &s;uch Principle, it being only an imaginary &s;ub&s;titution; and if it be any thing be&s;ides imagination, it &s;eems to be but Air, or at mo&s;t that &s;ubtler part
<PB N="124" REF="66">of the Univer&s;e called <HI>Aether,</HI> which po&s;&s;ibly may be nothing el&s;e but the &s;ubtler and more refined parts of the Air, di&s;gro&s;&s;ed of tho&s;e vapours or <HI>Efflu|via,</HI> which obtain ordinarily in the in|ferior parts of the Air, commonly cal|led the Atmo&s;phere.</P>
<P>And therefore one method of di&s;cu&s;|&s;ion of this que&s;tion will po&s;&s;ibly be ap|plicable to both the&s;e Suppo&s;itions, of the admi&s;&s;ion of forreign Air or <HI>Aether</HI> into the derelicted &s;pace in the Tube above the Mercury.</P>
<P>If therefore it be forreign Air or <HI>AE|ther</HI> that occupies that place, it mu&s;t be upon one of the&s;e accounts, <HI>viz.</HI> either that the Air or <HI>Aether,</HI> upon the account of its own &s;ubtlety and tenuity, freely and of its own accord pervades the Gla&s;s or the Body of the &s;ub&s;iding Mer|cury, and &s;o takes up the derelicted room; or el&s;e that although of its own accord it would not penetrate through either of tho&s;e two Bodies, yet that it is as it were forcibly &s;trained through the pores of the Gla&s;s or Mercury, and by the &s;ub&s;iding of the Mercury, and the
<PB N="125" REF="66">re&s;i&s;tence of Nature again&s;t Vacuity, percolated into that vacant &s;pace.</P>
<P>As to the former of the&s;e Solutions, it &s;eems altogether unrea&s;onable to ima|gine any free or uncon&s;trained penetra|tion of the Air, or <HI>Aether,</HI> into that &s;pace: for although the Gla&s;s, and like|wi&s;e the Mercury are not altogether de|&s;titute of Pores, yet they do not run in a &s;traight uninterrupted line, but are cro&s;&s;ed and ob&s;tructed by interpo&s;ed filaments, that mu&s;t nece&s;&s;arily &s;top the free pa&s;&s;age of the Air or <HI>Aether</HI> through them, &s;o that they are not wholly per|vious to tho&s;e Bodies.</P>
<P>And that this is &s;o, appears by this one in&s;tance, which is as good as a thou|&s;and.</P>
<P>If it were true, that the Air or <HI>Aether</HI> did freely pa&s;s through the &s;uppo&s;ed pores of the Gla&s;s or Mercury, the Mer|cury would never be &s;u&s;pended at twen|ty nine Inches, but would wholly &s;ink into the ve&s;&s;el or re&s;tagnant Mercury; for the in&s;inuation of the Air or <HI>Aether</HI> through the Gla&s;s or Mercury, would &s;upply the vacuity, as well below twen|ty
<PB N="126" REF="67">nine Inches as above, and &s;o accom|modate the derelicted &s;pace in all its E|vacuation, as well as in part, and like|wi&s;e would accommodate the Mercury in its natural de&s;cent without any in|convenience; and yet we find, that at twenty nine Inches the Meccury keeps up, and &s;ub&s;ides not.</P>
<P>And that which puts it out of que|&s;tion, that the natural irruption of the Air or <HI>Aether</HI> fills not this Space, is this: let but the lea&s;t orifice, no bigger than the point of a &s;mall Needle be made in the top of the Gla&s;s Tube, the Mercury would entirely de&s;cend, and not be &s;u|&s;tained at twenty nine Inches, becau&s;e here is an admi&s;&s;ion of forreign Air to &s;upply the &s;pace derelicted by the Mer|cury, as fa&s;t as it de&s;cends. And the &s;ame effect would follow, if the Air or <HI>Aether</HI> did penetrate through the &s;mall pores of the Gla&s;s or Mercury. And &s;ince we &s;ee it doth not obtain that effect, we have rea&s;on unque&s;tionably to conclude, it hath not any admi&s;&s;ion <HI>ab extra</HI> through tho&s;e &s;uppo&s;ed pores of either of tho&s;e Bodies.</P>
<PB N="127" REF="67">
<P>It remains therefore to be con&s;idered, whether that by the great contention of Nature again&s;t Vacuity, and the for|cible &s;tre&s;s of the Mercury on its de&s;cent downward, there be not a kind of for|cible &s;training of &s;ome Aery or Ethe|real Particles through the Gla&s;s, or at lea&s;t through the Mercury, which is partly expo&s;ed to the external Air.</P>
<P>I an&s;wer, fir&s;t, as touching the per|meating of Air or <HI>Aether</HI> through the Gla&s;s; it &s;eems utterly impo&s;&s;ible, for the rea&s;on before given. Indeed the vigor of Light or Fire penetrates the Gla&s;s, not (as it &s;eems) by any tran&s;ition of any Corporeal Sub&s;tance, but only of a <HI>vis, virtus,</HI> or <HI>vigor,</HI> which commu|nicates the quality of <HI>lumen</HI> or <HI>calor</HI> to the Body that it finds there, but conveys not any Corporeal Sub&s;tance tran&s;mit|ted through the Gla&s;s.</P>
<P>Secondly, as touching the &s;uppo&s;ed &s;training of the Air or <HI>Aether</HI> through the Mercury, and di&s;charging it in the &s;ummity of the Tube: I mu&s;t needs &s;ay, that in &s;ome in&s;tances the forreign Air will make a vi&s;ible perforation and
<PB N="128" REF="68">tran&s;ition through the body of Mercu|ry, as well as of Water.</P>
<P>If a Tube of Gla&s;s, &s;ealed at one end, be filled with Water, or Mercury, and then inverted in the free Air, (unle&s;s the Tube be extremely &s;mall) the Mer|cury will &s;ub&s;ide and de&s;cend by the &s;ides of the Tube, and the Air a&s;cend through it in a Pillar or Bubbles in the mid&s;t, in the very &s;ame &s;ucce&s;&s;ive order as the Mercury de&s;cends; the Mercury thus laterally de&s;cending, making way for the a&s;cent of the Air, and the Air in the &s;ame &s;ucce&s;&s;ive moments a&s;cending, filling the room relicted by the Mercu|ry: and this a&s;cent of the Air is evident and con&s;picuous to the Eye.</P>
<P>But in the matter in que&s;tion, there &s;eems to be no &s;uch pervading of the Air through the pores of the &s;u&s;pended or re&s;tagnant Mercury.</P>
<P>Fir&s;t, if &s;uch a tran&s;ition of the Air were through the column and re&s;tag|nant Mercury, it mu&s;t needs (as in the former ca&s;e) make a vi&s;ible appearance thereof in the Mercury, and rai&s;e &s;ome tumultuous <HI>phaenomena</HI> in it, but no &s;uch
<PB N="129" REF="68">thing appears to the eye in the <HI>Torricel|lian</HI> Experiment!</P>
<P>Secondly, the difficulty of the <HI>tran&s;i|tus</HI> of the external Air through the Mercury in the <HI>Torricellian</HI> Experiment is infinitely greater than in the in&s;tance above given: for in that in&s;tance the Air hath but one motion upward, and is a&s;&s;i&s;ted in it by the Mercury giving way to it. But here in the <HI>Torricellian</HI> Experiment, there mu&s;t be a double in|tention and motion of the Air, <HI>viz.</HI> 1. It mu&s;t <HI>de&s;cendendo</HI> terebrate through the re&s;tagnant Mercury, and then when it hath pa&s;&s;ed that difficulty, it mu&s;t tere|brate through the erect column of Mercury <HI>a&s;cendendo.</HI> And it is not con|ceptible that the pores of the erect and re&s;tagnant Quick-&s;ilver, cro&s;&s;ing one another in re&s;pect of their po&s;ition and &s;ituation, can accommodate &s;uch a crooked and contradictory motion of any particle of Air.</P>
<P>Thirdly, again it cannot rea&s;onably be thought, but that if there were &s;uch a tran&s;ition of the Air through the re|&s;tagnant, and &s;u&s;pended Quick-&s;ilver,
<PB N="130" REF="69">but it &s;hould be as rea&s;onabe to continue after the &s;ub&s;iding of the Mercury to twenty nine Inches, as before, the pa&s;|&s;age remaining &s;till open through the Mercury. The con&s;equence whereof would be, that the whole Tube would be &s;upplied with Air, and con&s;equently the whole body of Mercury be emptied into the re&s;tagnant ve&s;&s;el; as when a little Pin-hole is made in the top of the &s;ealed Tube.</P>
<P>Fourthly, again if it were forreign Air or <HI>Aether</HI> that were admitted, it is not ea&s;ily conceptible, how the finger &s;topping the upper orifice of the Tube, &s;hould be attracted inward, or the Blad|der di&s;tended, as in the former Chapter; for the immi&s;&s;ion of forreign Air through the Mercury, or Gla&s;s, mu&s;t rather contract than expand the Blad|der, by the acce&s;&s;ion of an external com|pre&s;&s;ion from it, as will happen upon the lea&s;t hole made in the Tube. Upon the&s;e and the like rea&s;ons it &s;eems to me altogether improbable, that the de|relicted &s;pace &s;hould be filled with Air or <HI>Aether</HI> from without, by an intro|mi&s;&s;ion
<PB N="131" REF="69">of it through the Gla&s;s or Mer|cury.</P>
</DIV2>
<DIV2 N="9" TYPE="chapter">
<HEAD>CHAP. IX</HEAD>
<HEAD TYPE="sub"><HI>Concerning the other Suppo&s;ition, namely, that this derelicted Space is filled with a Body <HI>ab intra.</HI></HI></HEAD>
<P>Since therefore I have concluded, that this derelicted Space in the Tube is filled with a Body, and that That Body comes not <HI>ab extra,</HI> and there is no Bo|dy within to &s;uppply that room but the Mercury, or that which mu&s;t be ex|tracted from it: and in as much as the Mercurial con&s;i&s;tence it &s;elf is de&s;cended to twenty nine Inches, it remains nece&s;|&s;ary that this Body that fills the dereli|cted <HI>inter&s;titium,</HI> mu&s;t be a &s;ubtle body extracted from the Mercurial body. But how, or in what manner this is ef|fected, is inquirable.</P>
<P>And now before I come to the Inqui|ry it &s;elf, I mu&s;t take notice that there are three kinds of in&s;tances of the <HI>Torri|cellian</HI> Experiment.</P>
<PB N="132" REF="70">
<P N="1">1. The fir&s;t is, where the Tube is ju&s;t twenty nine Inches and half long, and &s;ealed at the top, and then filled with Mercury, and inverted into re&s;tagnant Mercury, without any admi&s;&s;ion of any Air; and though that be difficult to effect, yet if it be effected, there is no va|cant &s;pace left, but the column of Mer|cury adheres to the top of the Tube, it being its ju&s;t &s;tation.</P>
<P N="2">2. The &s;econd is, when the Tube is above twenty nine Inches and half, &s;up|po&s;e four foot long, &s;ealed at the top, and filled up to twenty nine Inches and half, and then inverted, whereby the Air ri|&s;eth to the top of the Tube, and the Mercury &s;ub&s;ides not only to twenty nine Inches and half, but much lower, namely as far as that column of Air in the upper end of the Tube is by ten&s;ion extendible by the force of the de&s;cen&s;ion of the Mercury, which being about eighteen Inches of Air, po&s;&s;ibly by the de&s;cent of the Mercury will be extended to above twice the length, whereby the Mercury may &s;ub&s;ide it may be to about fourteen Inches, (I am not curious in the Calculation.)</P>
<PB N="133" REF="70">
<P N="3">3. The third In&s;tance is, where the Tube for the purpo&s;e is four foot long, &s;ealed at one end, filled with Mercury without any portion of Air admitted, whereby the Mercury inverted into a ve&s;&s;el of re&s;tagnant Mercury, &s;ub&s;ides to twenty nine Inches and half, and &s;o leaves about eighteen Inches de&s;erted by the Mercury.</P>
<P>And though in the pur&s;uit of this di&s;|cour&s;e there will be u&s;e of the di&s;cu&s;&s;ion of the two former In&s;tances, yet in this place only the la&s;t of the three yeilds the Inquiry, namely what it is that fills that &s;pace derelicted by the Mercury.</P>
<P>And I adventure to conclude, that it is a &s;ubtle Corporeal Sub&s;tance extra|cted from the gro&s;s Mercurial Body, or forced out of it.</P>
<P>The methods of this Separation are two, the one propo&s;ed by <HI>Linus,</HI> the other offered by others.</P>
<P>That of <HI>Linus</HI> (if I under&s;tand him aright) &s;eems to be this: namely that by the de&s;cent of the Mercury, and <HI>in ob&s;e|quium naturae univer&s;alis,</HI> for preventing of Vacuity, there are taken away &s;ucce&s;|&s;ively
<PB N="134" REF="71">from the &s;uperficies of the Mer|cury certain &s;cales as it were of an in|divi&s;ible profundity, and the&s;e are rari|fied into a &s;ubtle invi&s;ible con&s;i&s;tence or vapor, which &s;upply that de&s;erted &s;pace, and make up a kind of <HI>funiculus</HI> that &s;u&s;pends the Mercury to the Tube, and is coextended to the whole vacant &s;pace gradually, as the Mercury de&s;cended.</P>
<P>This &s;eems to be &s;omewhat difficult, e&s;pecially con&s;idering the heterogene|ous parts of the Mercury, whereof &s;ome &s;eem to be of that &s;olidity, that are un|capable of &s;uch a &s;eparation.</P>
<P>Be&s;ides it would be difficult to con|ceive, how the&s;e &s;uperficies of this Body &s;hould in a moment, by the inclination of the Tube, be rejoyned to the Mercu|rial body and con&s;i&s;tence; and in a moment again, upon the re-erection of the Tube to its perpendicular po&s;ture, be rarefied from &s;o gro&s;s a con&s;i&s;tence into &s;o &s;ubtle and invi&s;ible a nature; both which will be the effects, one of the inclination, the other of the re-ere|ction of the Tube.</P>
<P>Therefore I &s;hall rather choo&s;e ano|ther,
<PB N="135" REF="71">and, as I think a more accounta|ble Solution.</P>
<P>It is plain to our daily ob&s;ervation, that all Bodies, e&s;pecially &s;uch as are liquid or fluid, do continually &s;end out from them certain &s;ubtle <HI>Effluvia,</HI> &s;carce perceptible to the Eye, but manife&s;t in their effects. It is al&s;o evident, that all Bodies, e&s;pecially fluids, and &s;uch as con&s;i&s;t even of Heterogeneous parts, by &s;trong agitation, by heat or motion, have many of their parts re&s;olved into a more &s;ubtle con&s;i&s;tence, than appeared before &s;uch agitation. Thus Water by heat or violent motion re&s;olves it &s;elf into vapours or &s;teams.</P>
<P>Mercury is of it &s;elf an heterogeneous body, con&s;i&s;ting of &s;ome more &s;olid, o|ther more fluid and moi&s;t parts. If any man &s;hall take the pains violently to &s;hake Water and Mercury together, and throughly wa&s;h it, he &s;hall find the &s;hi|ning parts that are the more fluid, &s;e|vered from little black or dark granules like Sand, which will gradually &s;ub&s;ide vi&s;ibly in the water into a heap, before the nimble &s;hining particles united
<PB N="136" REF="72">to them, and al&s;o certain Airy corpu&s;cles ri&s;ing to the top of the Water.</P>
<P>And as thus by the &s;eparation by wa|ter, &s;o by a &s;trong heat the Mercurial Bodies will be in a great mea&s;ure re|&s;olved into a fume or &s;moak, which ne|verthele&s;s (as is &s;aid) will coagulate a|gain, and a&s;&s;ume the former Mercurial con&s;i&s;tency, at lea&s;t in a great mea&s;ure.</P>
<P>Mercury, though it be one of the col|de&s;t Minerals, doth contain and &s;end out from its body certain <HI>Effluvia,</HI> and noxious vapors, as they experiment that are conver&s;ant in Mines of that kind.</P>
<P>If any man ob&s;erve the de&s;cent of the Mercury from the top of a long Tube in the <HI>Torricellian</HI> Engine, he &s;hall find the de&s;cent not &s;o quick and nimble, as if both ends were open, and (contrary to the u&s;ual acceleration of de&s;cending heavy Bodies) more and more &s;low and faint, the nearer it comes to its &s;tation; which is an evidence that there is a <HI>luct a</HI> and contention in Nature, while it extrates, &s;eparates, and abrades the parts, that mu&s;t &s;upply the derelicted
<PB N="137" REF="72">&s;pace, and likewi&s;e in giving them a ten&s;ion or dilatation an&s;werable to it.</P>
<P>They that have exerci&s;ed much the <HI>Torricellian</HI> Experiments, and tho&s;e of the like nature with Mercury, have ap|parently found that the frequent itera|tion of the&s;e Experiments have much imba&s;ed the nature of Mercury, depu|rating it from tho&s;e &s;ubtle &s;teams and <HI>Effluvia</HI> that naturally attend it, and thereby the very Mineral it &s;elf becomes more vapid, di&s;charged of its &s;ubtle Spi|rits or parts, and rendred le&s;s u&s;eful not only for Medicinal but Mechanical Experiments: whereby it appears that it lo&s;eth &s;omewhat of its more &s;ubtle &s;ub|&s;tance by iterated Experiments, and will prove more &s;luggi&s;h. For this I call to witne&s;s <HI>Honoratus Fabri,</HI> in the latter end of his <HI>Philo&s;ophical Dialogues,</HI> and &s;ome of our own Nation that have a&s;&s;erted the &s;ame, and in my own Ex|perience I have al&s;o found it true.</P>
<P>It is certain, that when Mercury, or any other fluid falls in a Tube, the high|er it falls, the more force it hath, and the greater compre&s;&s;ion the lower parts
<PB N="138" REF="73">receive from the upper; for all Bodies that de&s;cend, de&s;cend with the greater force, according to the altitude of their de&s;cent, as I &s;hall have occa&s;ion hereaf|ter to ob&s;erve.</P>
<P>The de&s;cent therefore of Mercury in a Tube of &s;ix foot high, is much more powerful than a de&s;cent from four foot high; and That than a de&s;cent from three foot, or twenty nine Inches high, and con&s;equently the compre&s;&s;ion of the inferior parts by the &s;uperior; and in a greater de&s;cent than in a le&s;s. the agitation of all is the more vigorous</P>
<P>And yet (as I before &s;aid) it is evident in the de&s;cent of the Mercury from a Tube of four foot high, &s;topt above, and im|mer&s;ed beneath in re&s;tagnant Mercury, is not without a <HI>lucta</HI> or contention; and although the higher the Tube is, the de&s;cent at fir&s;t is more quick, yet it gradually grows &s;lower and &s;lower, 'till it come to the common &s;tation of its &s;u&s;pen&s;ion, <HI>viz.</HI> twenty nine Inches and half, or thereabouts. But yet even in the fir&s;t efforts of its motion, it is not &s;o quick or violent, as its own natural
<PB N="139" REF="73">motion would otherwi&s;e attain for it, receives a <HI>remora</HI> and impediment by the difficulty of &s;eparating of its &s;ubtle parts.</P>
<P>The&s;e things are apparently true to any man's ob&s;ervation, and from the&s;e ob&s;ervations I frame the&s;e Conclu&s;ions.</P>
<P N="1">1. That the &s;ub&s;tance that fills the head of the Tube, as the Mercury de|&s;cends, are the <HI>Effiuvia,</HI> &s;teams, or &s;ub|tle vaporous parts of the Mercurial Body.</P>
<P N="2">2. That the&s;e &s;teams or vapors are &s;eparated from the Mercurial body by a double immediate means. Fir&s;t by way of Expre&s;&s;ion, or driving them out by the &s;trong de&s;cending motion of the Mercury, the compre&s;&s;ion of the inferior parts by the &s;uperior, and the great agi|tation of its parts; the gro&s;&s;er Mercu|rial parts coming clo&s;er together, and driving out the more &s;ubtle and vapo|rous parts. Secondly by way of Ex|traction, or &s;training out tho&s;e parts that are more &s;ubtle and fluid, and ca|pable of Expan&s;ion, and from hence ari&s;eth that <HI>lucta</HI> and <HI>mora</HI> in the de&s;cent
<PB N="140" REF="74">of the Mercury, by the &s;training of the Mercurial vaporous bodies, and raking them out. And</P>
<P N="3">3. That tho&s;e parts thus extracted are dilated and extended to as great an amplitude and ten&s;ion, as the &s;trength of the de&s;cent of the Mercury, and the amplitude of the &s;pace it leaves re|quires; which ten&s;ion al&s;o contributes much to the retarding of the &s;wiftne&s;s of the Mercurial de&s;cent.</P>
<P N="4">4. And becau&s;e at twenty nine In|ches and half, the weight of the Mer|cury decrea&s;eth to &s;uch a &s;tate, as cannot work any farther &s;eparation of &s;ubtle matter to &s;upply any more room, it &s;tays there, and de&s;cends no farther, not having &s;trength enough at that hight to &s;eparate any &s;ubtle matter from it &s;elf, to &s;upply the &s;pace it &s;hould leave by &s;uch de&s;cent.</P>
<P N="5">5. Although the immediate cau&s;e of the &s;eparation of the &s;ubtle matter of Mercury, and the expan&s;ion or dilata|tion thereof, be the force of the de&s;cent, and weight, and pre&s;&s;ure of the Mercu|ry, yet this is performed <HI>in ob&s;equium
<PB N="141" REF="74">univer&s;alis naturae,</HI> for the avoiding of the di&s;&s;olution of Continuity, or, which is all one, <HI>obfugam vacui.</HI></P>
<P N="6">6. And the &s;ame rea&s;on <HI>mutatis mu|tandis</HI> will be applicable to the &s;u&s;pen&s;i|on of water in a Tube, which will be &s;u&s;|pended at 31 foot, or thereabout, as Mer|cury is at twenty nine Inches. For by the &s;ame means that &s;ubtle parts are &s;epa|rable from Mercury, &s;ubtle parts are much more &s;eparable from Water, by a &s;trong ten&s;ion or compre&s;&s;ion of it, as appears by the rai&s;ing of innumerable Airy Bubbles out of a ve&s;&s;el of Water, by the &s;trong ten&s;ion of the Air in the Air-pump, large in&s;tances whereof ap|pears in Mr. <HI>Boyle's</HI> Experiments, 19, 21, 22, 23, <HI>&amp;c.</HI></P>
<P>The whole proce&s;s and model of the &s;u&s;pending of Water in a long Tube above one and thirty foot long, and how it &s;ub&s;ides to about one and thirty foot, and no longer. <HI>vide apud Shottum</HI> in his <HI>mirabilia Vari lib. 3. cap. 2. in Ex|perimento Robervalli Magnani &amp; Bertii.</HI></P>
<P>And now if it be &s;aid, &s;uppo&s;e the Tube were &s;even, eight, or ten foot
<PB N="142" REF="75">long, or if it were three or four foot long, and the upper end were a Bolts head, that &s;hould contain three or four pound of Mercury, this would &s;ub&s;ide to twenty nine Inches: where &s;hould there be <HI>Effluvia</HI> to fill &s;o great a &s;pace?</P>
<P>I an&s;wer: the more Mercury de&s;cends to twenty nine Inches, the more <HI>Efflu|via</HI> there will be to fill that place that the Mercury left, and &s;o the Supply will nece&s;&s;arily be as liberal, as the &s;pace the Mercury took up before its de&s;cent to 29 Inches and half, becau&s;e there is a grea|ter &s;tock of Mercury to yeild it, and a greater continuation of motion to ex|tract it. And there &s;eems no nece&s;&s;ity of any great quantity of &s;ubtle matter to be driven, or driven out of the Mer|curial Ma&s;s, becau&s;e it is a &s;ub&s;tance ca|pable of dilatation to a greater expan|&s;ion than its own natural con&s;i&s;tency, by the &s;ub&s;iding of the Mercury.</P>
<P><HI>Mer&s;ennus</HI> tells us, that by experience he finds, that by a &s;trong ten&s;ion of a particle of Air, it is capable to an ex|pan&s;ion of neer &s;eventy times the &s;pace of its ordinary con&s;i&s;tency, as in Aeoli|piles,
<PB N="143" REF="75">and the like Engins. And we &s;ee that if an Inch of Air be left in the top of the Tube, it will by the bare force of the de&s;cent of the Mercury be expanded to neer ten times its former &s;pace. And upon the &s;ame account it will fall out, that the quantity of one Inch of tho&s;e Mercurial effluxes will, by the de&s;cent of the Mercury, be &s;tretched out and ex|panded to fill the derelicted &s;pace of the Mercury, far exceeding their common and ordinary exten&s;ion.</P>
<P><HI>Fig. 9.</HI> The mo&s;t con&s;iderable Ob|jection again&s;t this Suppo&s;ition &s;eems to be this. That if the Tube of four foot long filled with Mercury, and then im|mer&s;ed in re&s;tagnant Mercury, where|by the Mercury &s;ub&s;ides to twenty nine Inches, and leaves a &s;pace of about 18 Inches &s;eemingly empty, yet if the Tube be inclined, as in <HI>B,</HI> to an altitude pa|rallel to twenty nine Inches of vertical hight. The Tube <HI>B</HI> will be as at fir&s;t filled with Mercury, drawn or driven out of the re&s;tagnant ve&s;&s;el, and no va|cant &s;pace left; and if again it be ere|cted perpendicularly as before, the Mer|cury
<PB N="144" REF="76">will &s;ub&s;ide as before, <HI>viz.</HI> to twen|ty nine Inches; what becomes of the &s;ubtle exhalation upon the inclination of the Tube?</P>
<P>I an&s;wer, it is true, that by the incli|nation of the Tube the Mercury that de|&s;cended out of the. Tube into the re|&s;tagnant ve&s;&s;el of Mercury, will be drawn up into the Tube, and the Tube filled again with it, the &s;ame by the in|clination of the Tube becomes of le&s;s accidental weight. But this doth no way cro&s;s what I have &s;uppo&s;ed: I therefore an&s;wer,</P>
<P N="1">1. That by the inclination of the Tube at <HI>B,</HI> the Mercury doth not pre&s;s &s;o urgently upon the &s;ubjected Mercury, as it doth in its perpendicular po&s;ition; for it is &s;u&s;tained according to the laws of Staticks by leaning upon the incli|ned Tube, and pre&s;&s;eth not &s;o forcibly upon the fund or Ba&s;e.</P>
<P N="2">2. That therefore the pores or con|&s;i&s;tency of the Mercury in the inclined Tube are more lax and open, and regain more of that natural texture of its Mer|curial con&s;i&s;tence, and receives into it
<PB N="145" REF="76">again tho&s;e connatural &s;teams or efflu|xes, that were &s;hot or drawn out of it by its former compre&s;&s;ion, and the attra|ction made upon it by rea&s;on of its de|&s;cent.</P>
<P N="3">3. And by its re-erection unto its former perpendicular po&s;ture, they are again thru&s;t or drawn out by its con|traction and compre&s;&s;ion, and the for|cible attraction wrought upon it by that Catholick Law of Nature, pre&s;er|ving the continuity of the Univer&s;e.</P>
<P>And that which &s;eems evidently to evince the truth hereof, is the in&s;tance given by the Excellent Author him&s;elf, in his 20, 21, 22, 23, but e&s;pecially in his 24^th Experiment of the Air-pump; wherein the violent attraction of the Pump, and the &s;trong ten&s;ion of the Air included in the Receiver, rai&s;eth from the bottom of an included ve&s;&s;el of Wa|ter Oyl, but e&s;pecially Spirit of Wine, great Bubbles to the top of the ve&s;&s;els, (which is performed either by that for|cible extraction of the more &s;ubtle and Aerial Particles included in that liquor, or by &s;ubtilizing or rarefying &s;ome
<PB N="146" REF="77">parts of the liquor. But as &s;oon as that &s;trong ten&s;ion and attraction by the included Air is taken off, by the immi&s;|&s;ion of fre&s;h Air into the Receiver, the Bubbles &s;ub&s;ided, and the &s;ubtle parts included in it were again rejoined, and reunited to the &s;ame liquors from whence they were exhau&s;ted, which by a new ten&s;ion wrought by a new re|peted &s;uction of the Pump, might be again extracted.</P>
<P>And thus far touching the third Ge|neral, namely what it is that is inclu|ded in the &s;pace derelicted by the Mer|cury.</P>
</DIV2>
<DIV2 N="10" TYPE="chapter">
<PB N="147" REF="77">
<HEAD>CHAP. X.</HEAD>
<HEAD TYPE="sub"><HI>The enquiry touching the Cau&s;e that keeps the Mercury &s;u&s;pended in the Tube at 29 Inches, or there about; and fir&s;t what is not the Cau&s;e of this Su&s;pen&s;ion.</HI></HEAD>
<P>THE con&s;ideration of what it is that remains in the derelicted &s;pace, in the upper end of the Tube, and the con&s;ideration what it is, that keeps up the Mercury to twenty nine Inches, or thereabouts, are of two &s;everal kinds: for although the former Con&s;ideration is nece&s;&s;ary to be known, before we can arrive at a rea&s;onable di&s;covery of the latter; yet it would not be &s;imply of it &s;elf impo&s;&s;ible, that there &s;hould be &s;uch a corporeal &s;ub&s;tance, as I have above conjectured, in the derelicted head of the Tube, and yet the Mercury might wholly di&s;charge it &s;elf in the re&s;tag|nant ve&s;&s;el, which yet we &s;ee it doth not.</P>
<P>Therefore having in the former
<PB N="148" REF="78">Chapters fini&s;hed the former, which was the fourth general Inquiry, name|ly, what it is that fills the derelicted &s;pace; I now come to the fifth and &s;ixth Inquiry, namely what is not the cau&s;e of this &s;u&s;pen&s;ion of the Mercury, and what &s;eems to me the true cau&s;e thereof.</P>
<P>And among tho&s;e that are a&s;&s;igned for cau&s;es of this &s;u&s;picion, which yet are not cau&s;es thereof, I &s;hall mention on|ly the&s;e three; namely the renitence or re&s;i&s;tance of the Mercury in the re&s;tag|nant ve&s;&s;el; 2. and the counterpoi&s;e of the impendent column of the Atmo|&s;phere, equal in ba&s;e to the ba&s;e of the Cylinder of Mercury &s;u&s;pended in the Tube; and 3. the Elatery or Spring of the inferior part of the Air.</P>
<P>Of the former briefly in this Chapter, of the two latter more at large in what follows.</P>
<P><HI>Stevinus</HI> in the Explication of the 10^th Propo&s;ition of his Hydro&s;taticks, a&s;&s;irms, that the re&s;i&s;tence of the ba&s;e of any fluid Body, is greater in propor|tion than the <HI>pondus deprimens</HI> of a like
<PB N="149" REF="78">fluid: which <HI>Fabri</HI> in the &s;ixth of his <HI>Philo&s;ophical Dialogues, pag.</HI> 480. and 493, goes about Geometrically to demon|&s;trate: but I confe&s;s that it is performed with &s;o much intricacy, and ob&s;curity, that I do not fully apprehend it.</P>
<P>And if this be &s;o, it may &s;eem at fir&s;t view, that the re&s;i&s;tance of the re&s;tag|nant Mercury in the &s;ubjacent ve&s;&s;el, which is as it were the ba&s;e or foot of that Mercurial Column of Mercury, that is &s;u&s;pended in the Tube, may con|tribute &s;omething to its &s;u&s;tentation in that po&s;ition.</P>
<P>But upon due con&s;ideration I find this is but an imagination, and contri|butes nothing to this <HI>phaenomenon.</HI></P>
<P>Indeed, if a liquid be impendent upon &s;olid ba&s;e, as Mercury upon Marble; or if a lighter or le&s;s compacted fluid be bot|tomed or imba&s;ed upon a much more gro&s;s and compacted fluid, as a Tube full of Air upon a Superficies of Water, or a Tube full of Water upon a Superficies of Mercury, though the Tube be open at both ends, the Ba&s;e will &s;u&s;tain the Column of the lighter or le&s;s compacted fluid.</P>
<PB N="150" REF="79">
<P>But if they are of the &s;ame kind and con&s;i&s;tence, the Ba&s;e contributes no|thing to the &s;u&s;tentation of the impen|ding Column. But if there be no other impediment, it will wholly &s;ub&s;ide. And therefore if a Tube, open at both ends, be filled with Water, and the lower end &s;topt with the finger, be immer&s;ed under a ve&s;&s;el of Water, and then un&s;topped; or if an open Tube &s;topt at the lower end with the finger, be immer&s;ed in a ve&s;&s;el of re&s;tagnant Mercury; in the former ca&s;e the Water, and in the latter the Mercury will wholly &s;ub&s;ide to the level of the Super|ficies of the Water or Mercury in the &s;ubjacent ve&s;&s;el, which would not be, not with&s;tanding the Tube were open at both ends, if a Ba&s;e of the &s;ame fluid had any force or re&s;i&s;tance again&s;t its de&s;cent.</P>
<P>Nay the truth is, the po&s;ition of the Water or Mercury in the Tube, in any the lea&s;t degree higher than the Super|ficies of the Water or Mercury in the ve&s;&s;el, hath an accidental Gravitation upon a lower Superficies of the &s;ame
<PB N="151" REF="79">fluid, by rea&s;on of &s;uch po&s;ition or ele|vation of the fluid in the Tube, above the Superficies of the fluid in the ve&s;&s;el, and by that po&s;ition pre&s;&s;eth upon it, as &s;hall be farther illu&s;trated hereafter. And therefore the <HI>pondus deprimens</HI> of the &s;ame fluid in &s;uch an elevated po&s;i|tion, conquers and overmatcheth the <HI>potentia &s;u&s;tinens</HI> of the &s;ubjected fluid, though it were an Ocean of Water. I therefore lay a&s;ide this Suppo&s;ition, as contributing nothing to this <HI>phaenome|non,</HI> and proceed to the examining of tho&s;e, that with great preten&s;ion and patronage are &s;ugge&s;ted to be the Cau&s;e of this Su&s;pen&s;ion.</P>
</DIV2>
<DIV2 N="11" TYPE="chapter">
<PB N="152" REF="80">
<HEAD>CHAP. XI.</HEAD>
<HEAD TYPE="sub"><HI>Concerning the &s;uppo&s;ition of the <HI>aequipon|dium</HI> of a pillar of the Air, or Atmo|&s;phere, as the Cau&s;e &s;u&s;taining the Mer|curial Cylinder.</HI></HEAD>
<P>THis latter age, as it produced the <HI>Torricellian</HI> Experiment, &s;o it hath produced a new Sy&s;teme in Nature for the Solution of it, namely the Gravi|tation of the Atmo&s;phere, and an <HI>aequi|pondium</HI> of a Column thereof to the weight of the Mercurial Cylinder con|tained in the Tube, whereby it is &s;u&s;tai|ned; a fuller Explication whereof here|after follows.</P>
<P>And it is admirable to &s;ee, how much this new opinion hath, obtained among the <HI>Virtuo&s;i</HI> of this latter Age; &s;o that as a new fa&s;hion is greedily entertained a|mong the Gallants of the times, and an old fa&s;hion de&s;pi&s;ed and contemned; &s;o this new <HI>hypothe&s;is</HI> is as greedily enter|tained by the great Wits of the times,
<PB N="153" REF="80">and hath obtained the &s;tile of a <HI>Doctrine;</HI> and the Old Peripatetical Learning, touching <HI>Vacuum,</HI> and the In&s;eparabili|ty of Bodies, exterminated, under the re|proach of <HI>decantata fuga.</HI></P>
<P>Nay the theory is &s;o much idolized, that &s;ome late Authors have &s;trangely contended for the dignity of being the fir&s;t Inventers of it.</P>
<P>And &s;ome that have defended the Peripatetical Solution of <HI>fugavacui,</HI> as <HI>Shottus,</HI> when he wrot his <HI>mirabilia Hy|draulica</HI> and <HI>pneumatica;</HI> yet whether overwhelmed and a&s;toni&s;hed with the <HI>Magdeburgh</HI> Experiment and varieties thereof, or whether he was not willing to &s;eem to perceive le&s;s than the <HI>Virtuo&s;i,</HI> that had e&s;pou&s;ed the new Solution, becomes a Convert, and fairly retracts his former Opinion, and gives up the Solution of the <HI>Torricellian</HI> Experiment to the <HI>aequipondium</HI> of the like portion of the Atmo&s;phere, in his <HI>Technica Curi|o&s;a, l.</HI> 4. <HI>cap.,</HI> 6. &sect;. 2.</P>
<P>And 'tis plea&s;ant to &s;ee what a won|derful progeny, and voluminous Sy|&s;tems of Theories, Con&s;ectaries, and
<PB N="154" REF="81">Conclu&s;ions have been &s;ince built upon this Suppo&s;ition! wherein though the Authors have &s;hewn much wit, &s;ubtle|ty, and learning, yet they have lo&s;t the expence of much time, and invention, and pains, if at la&s;t when all is done, it prove but an imagination.</P>
<P>The Suppo&s;ition therefore &s;eems to be this:
I. That the Atmo&s;phere or lower portion of the Air, &s;ome &s;ay &s;even, &s;ome twenty two, others fifty, others an hun|dred miles high, hath a con&s;iderable Gravitation upon its inferior parts upon the Earth, and upon all Bodies in this lower world.</P>
<P N="2">2. That where a Tube, &s;ealed at one end, is filled with Mercury, and then inverted into a re&s;tagnant ve&s;&s;el of Mercury, the Mercury will &s;ub&s;ide to twenty nine Inches and half, and no lower, becau&s;e a column of Atmo&s;phe|rical Air, of the &s;ame ba&s;e with the ca|vity of the Tube, and incumbent upon the face of the re&s;tagnant Mercury, doth ju&s;t counterpoi&s;e &s;uch a column of Mer|cury of twenty nine Inches and half
<PB N="155" REF="81">high: &s;o that if the Mercurial Cylinder be of that bulk, as to weigh five pound, the Atmo&s;pherical Cylinder weighs ju&s;t as much, and &s;o as one artificial &s;cale being charged with an equal weight with the other, &s;tands in this <HI>aequilibri|um:</HI> &s;o in this natural Scale the Atmo|&s;pherical Cylinder pre&s;&s;ing upon the re&s;tagnant Mercury with an equal weight, to the 29 Inches and half of Mercury in the Tube, &s;u&s;tains and keeps it up in an <HI>aequilibrium.</HI></P>
<P N="3">3. But if while the Mercurial Cy|linder &s;tands thus &s;u&s;pended, there be any little hole made in the &s;ealed top of the Tube, the weight of the Air now pre&s;&s;ing in upon the Mercurial Cylin|der, takes away that <HI>aequilibrium</HI> which it had with that external column of At|mo&s;phere, while it was protected from the impendent column of Air by the &s;ealed top of the Gla&s;s; and now the Mercury is driven down by the equal weight of the Air, and wholly &s;ubfides into the re&s;tagnant Mercury; for now the Aereal Cylinder without the Tube, and that within and upon the Tube,
<PB N="156" REF="82">have the &s;ame common weight or Gra|vitation upon the Mercury. And upon the&s;e Suppo&s;itions they graft innumera|ble Conclu&s;ions, and among the re&s;t that the Air gravitates upon all Bodies; that the exact proportion of the weight of Air is herehence nece&s;&s;arily deduci|ble; for if a column of Mercury, of half an Inch diameter, and twenty nine In|ches and half high, weighs two pound (for in&s;tance,) then a column of Air of the &s;ame diameter, extending from the re&s;tagnant Mercury to the top of the Atmo&s;phere, weighs ju&s;t as much. And from hence they mea&s;ure the hight of the Atmo&s;phere, or ponderous Air; namely, Air being about a thou&s;and times lighter than the like bulk of Wa|ter, and Water being fourteen times lighter than the like bulk of Mercury, it mu&s;t follow by the rule of proportion, That if two pound of Mercury give a column of half an Inch diameter, to be twenty nine Inches high; then two pound of Atmo&s;phere mu&s;t give a co|lumn of twenty nine times 14000 Inches high: (I am not curious in the
<PB N="157" REF="82">proportion, but only &s;hew the method of their inferences:) and abundance of &s;uch fine Con&s;equences are built upon this Platform, which were too large to enumerate.</P>
<P>Now as touching this Solution of the Su&s;pen&s;ion of the Mercury in the Tube, by the <HI>aequipondium</HI> of a Cylinder of Air, of the &s;ame diameter with the Cylinder of Mercury, I &s;ay it &s;eems to me an Imagination, and to be utterly un|true.</P>
<P>I will not repete what I have former|ly &s;aid again&s;t the Gravitation of the Air, in the fourth Chapter, which yet I take to be &s;ufficient to evince the un|truth of this Suppo&s;ition: but I will &s;ubjoin two or three homely Experi|ments, which with the application of them will, as I think, detect the untruth and inefficacy of this Solution.</P>
<P N="1">1. I will begin with one offered by the A&s;&s;erters them&s;elves of this Solu|tion, of a late learned Author, in the 11. Propo&s;ition of his <HI>Hydro&s;taticks,</HI> and the <HI>Scholium</HI> thereupon, which I &s;hall agree to be a true Experiment, but the appli|cation
<PB N="158" REF="83">thereof too much di&s;torted, to gratifie the <HI>hypothe&s;is,</HI> but in truth and reality utterly confounding it.</P>
<P>Take a ve&s;&s;el of reftagnant Mercury, of &s;even Inches deep; then take a Gla&s;s Tube of half an Inch diameter in the cavity, and of half an Inch thick in each &s;ide, &s;ealed at the one end, and of 3 foot long; whereby the entire Tube will be an Inch and a half in its whole diameter: Fill it with Mercury, and &s;top it with the finger at the open end, and invert and immer&s;e it to the bottom of the re&s;tagnant Mercury. It will then come to pa&s;s, that about twenty nine Inches and half, the ordinary altitude of the column of Mercury, will be above the Superficies of the re&s;tagnant Mer|cury, and the whole Tube will thereby remain full to the top: but the Gla&s;s being lighter than the Mercury, will be impelled up by the re&s;tagnant Mercury neer to the Superficies thereof, where|by there will remain about &s;ix Inches of the upper end of the Tube empty of the Mercury, but &s;till there will be about twenty nine Inches and half of the Tube
<PB N="159" REF="83">&s;till full of Mercury, namely, the u&s;ual &s;tation of its Su&s;pen&s;ion.</P>
<P>I will &s;uppo&s;e the twenty nine Inches and half of Mercury, &s;u&s;pended in the Tube, to weigh one pound, and that the Gla&s;s Tube of it &s;elf weighs likewi&s;e one pound.</P>
<P>I will now &s;uppo&s;e, that the upper end of the Tube were fixed by a &s;tring to the Beam of a pair of Scales, as in his 319th figure in that book. I &s;ay that two pound in the adver&s;e Scale will counterpoi&s;e this Tube with the inclu|ded Mercury, and if any little advantage of weight, &s;uppo&s;e an Ounce, were ad|ded to the adver&s;e Scale, that Scale charged with two pound and an Ounce, will preponderate it.</P>
<P>And I &s;ay no more than what the Author &s;ays was determined touching it by the <HI>Royal Society,</HI> whereunto he &s;ub&s;cribes, <HI>pag.</HI> 727. in the&s;e words. <Q><HI>Pon|dus in adver&s;a lance contraponderans aequi|pollebat &s;u&s;pen&s;i hydrargyri cuju&s;ounque al|titudinis, at que &s;imul (quantum conjectando ae&s;timabant) &s;u&s;pen&s;i tubi ei parti quae &s;tag|nantis in &s;ubjecto va&s;e hydrargyri &s;uperfi|ciei
<PB N="160" REF="84">&s;upereminebat.</HI></Q> Now it is certain that if the one pound of Mercury con|tributes to this weight, it is not &s;u&s;tain|ed by the adjacent external column of Air, pre&s;&s;ing the Superficies of the re|&s;tagnant Mercury; for if &s;o, it is &s;u&s;tain|ed by the <HI>aequipondium</HI> of that Aereal co|lumn, and cannot affect the Scale with its weight; for it is &s;u&s;tained by ano|ther counterpoi&s;e, and not by the two pound weight of the Scale.</P>
<P>And again it is as certain, that if the Mercury do contribute to the counter|poi&s;e of the Scale, it mu&s;t by &s;ome means be as it were fa&s;tned to the Scale, (we will &s;uppo&s;e it to be <HI>Linus</HI> his <HI>funiculus,</HI>) for otherwi&s;e the Gla&s;s would only weigh as a &s;eparate thing from the Mercury, which would of it &s;elf contri|bute (<HI>ex &s;uppo&s;itione</HI>) but one pound to the weight, which would be nece&s;&s;ari|ly preponderated by the adver&s;e Scale charged with two pound weight.</P>
<P>And therefore it is mo&s;t clear, if the included column of Mercury contri|butes one pound weight to the ballance, it is not &s;u&s;tained by the imaginary
<PB N="161" REF="84">column of Air equal in diameter to the Mercurial Cylinder, but by an intrin|&s;ick connection or ligament to the Tube, whereby it weighs as one con|crete Body with the Gla&s;s, which I call the <HI>Funiculus ex &s;ubtilibus Mercurialibus effluviis contextus.</HI></P>
<P>The Author, to avoid this difficulty, therefore tells us, that this thing <HI>primo a&s;pectu incautis nonnullis ad Staticam mi|nus attentis facile imponeret;</HI> and to avoid the impo&s;ture, tells us, that all this while it is not the Mercury that contri|butes to the weight, for that hath ano|ther kind of Su&s;tentation by the <HI>aequi|pondium</HI> of the forreign Air; but it is another column of Air, that impends upon the upper end of the Gla&s;s Tube as its Ba&s;e, and therefore commen&s;urate to the &s;u&s;pended Mercury in weight. And this is the effect of the Solution, namely, that only the Gla&s;s, and the co|lumn of Air impendent upon it, makes the counterpoi&s;e, and the Mercury con|tributes nothing to it.</P>
<P>And indeed if the column of Air, charging the Tube, were of an equal
<PB N="162" REF="85">diameter with the Mercury, or the ca|vity of the Tube, the Eva&s;ion were hand&s;ome and &s;uitable to their <HI>hypothe&s;is,</HI> though untrue: but the in&s;tance in que&s;tion, as it is propo&s;ed, quite &s;hat|ters this Solution, and renders it not on|ly untrue, but un&s;uitable to their very principles.</P>
<P>For in this in&s;tance, the diameter of the column of Mercury is but half an Inch, but the diameter of the whole Tube is an Inch and half, which gives an <HI>area</HI> to the ba&s;e of the Cylinder of Air impending on it, more than four times bigger than the Ba&s;e of the Mercurial Cylinder. And therefore if a Cylin|der of the Atmo&s;phere of half an Inch diameter, be commen&s;urate to the weight of the Mercurial Cylinder, and con&s;equently weighs a full pound at that &s;cantlet; the Aereal Cylinder, commen&s;urate to the upper <HI>area</HI> of the Gla&s;s tube, which is an Inch and half diameter, mu&s;t nece&s;&s;arily weigh above four pounds, and therefore would not be equiponderated by the two pound weight in the oppo&s;ite Scale.</P>
<PB N="163" REF="85">
<P>This in&s;tance therefore which is de|livered with the memorial of the day, and place of its Exhibition, &s;eems to make more to the di&s;advantage, than the advantage of this new Philo&s;ophy.</P>
<P>But to this Objection there is a Solu|tion offered, namely, that let the Gla&s;s be of what thickne&s;s it will, That alters not the ca&s;e; for the Mercury is pre&s;&s;ed up by the counterpoi&s;e of a Cylinder of Air, an&s;werable to the cavity of the Tube, not to the cra&s;&s;itude of its &s;ides: for Gla&s;s being a Body &s;pecifically lighter than the Mercury, the Gla&s;s it &s;elf is &s;u&s;tained by the re&s;tagnant Mer|cury, which is its Ba&s;e, and &s;upports it.</P>
<P>But &s;till this An&s;wer, though it be true, avoids not the Objection. For 1. let us &s;uppo&s;e, in &s;tead of a Tube of Gla&s;s, a Tube of Gold, which being &s;pe|cifically heavier than &s;o much Mercury, would &s;ink to the bottom, and not be &s;u&s;tained by the Mercury, but mu&s;t be lifted up, and &s;u&s;tained purely by the weight in the oppo&s;ite Scale: 2. or &s;uppo&s;e the Tube of Gla&s;s were charged in its clo&s;ed end with a greater quantity
<PB N="164" REF="86">of Lead, that, though &s;pecifically lighter than Mercury, would by its exce&s;s of extrin&s;ical weight, depre&s;s the Tube to the bottom of the re&s;tagnant Mercury: or 3. though the Tryal were made by a Gla&s;s Tube filled with Water, and in|verted into a ve&s;&s;el of Water; for there the Gla&s;s Tube, with the inclo&s;ed Cy|linder of Water, would &s;ub&s;ide to the bottom, being altogether in its con|crete heavier than the Water, and could not be &s;upported by the re&s;tagnant Water, but by the weight in the adver&s;e Scale: in the&s;e In&s;tances the difficulty will not be &s;alved.</P>
<P>Therefore I took a Gla&s;s Tube, the cavity whereof was half an Inch diame|ter, the thickne&s;s of the Gla&s;s incircling the cavity <GAP DESC="math">of an Inch; and con&s;e|quently from out&s;ide to out&s;ide the dia|meter of the Tube was &frac58; of an Inch; the length of the Tube eighteen Inches, the weight thereof in the Air two oun|ces &frac34; of an Ounce, and being heavier than the like bulk of Water, it would freely &s;ub&s;ide perpendicularly to the bot|tom of a ve&s;&s;el of re&s;tagnant Water
<PB N="165" REF="86">deeper than 18 Inches, notwith&s;tan|ding the &s;u&s;tentation it had by the in|cluded Air, being empty, and &s;o the Water contributed nothing to the &s;up|port of the Tube when it came to be weighed, but only the thickne&s;s of its <HI>medium,</HI> which yet was not able to &s;up|port it from &s;inking.</P>
<P>The Water which the Tube would contain, weighed one Ounce and three quarters, wanting about a Grain or two at mo&s;t.</P>
<P>The Tube was tied at the clo&s;ed end with a &s;tring to the Scale of a Ballance and filled with Water, and &s;topping it with the finger, inverted into a ve&s;&s;el of Water 18 Inches deep, or more: and then the Tube with the included Wa|ter thus immer&s;ed in Water, carefully weighed, the Water &s;till remaining &s;u&s;|pended in the Tube, (as it will do as long as it &s;tands &s;o immer&s;ed,) and the Events were the&s;e: When the Tube was full &s;ix Inches above the Superficies of the Water in the Ve&s;&s;el, it weighed ju&s;t two Ounces and three quarters of an Ounce, which
<PB N="166" REF="87">weight in the oppo&s;ite Scale kept it in an <HI>equilibrium;</HI> for now the re&s;t of the Water in the Tube, below the Superfi|cies of the Water in the ve&s;&s;el, weighed nothing at all, becau&s;e it obtained &s;o far the &s;ame common Superficies, and was therefore &s;u&s;tained by the common weight which it had with the Water in the ve&s;&s;el, and only &s;ix Inches of Water contributed to the counterpoi&s;e, toge|ther with the weight of the Gla&s;s Tube it &s;elf, though refracted by the thick|ne&s;s of the <HI>medium:</HI> &s;o that now the&s;e &s;ix Inches of &s;u&s;pended Water, and the Tube it &s;elf, weighed no more at this po&s;ition in the Water, than what the Tube alone weighed in the Air.</P>
<P>But when the Tube, with the inclu|ded column of Water was rai&s;ed very neer eighteen Inches above the Super|ficies of the ve&s;&s;el of Water, &s;o that there was as little as could well be to keep the orifice of the Tube under Water, <HI>viz.</HI> about a quarter of an Inch, it then required an addition of very neer one Ounce &frac34; in the oppo&s;ite Scale, to hold the Tube in an <HI>aequilibrium</HI> which equal|led
<PB N="167" REF="87">the true weight of the Tube it &s;elf and Water included, when in the free Air, <HI>viz.</HI> two Ounces and three quar|ters, and one Ounce and three quarters, in all four Ounces and half; becau&s;e now the Water in the Tube had now in effect its due weight, which it had when divided from the Water in the ve&s;&s;el, and &s;o had its due Gravitation upon the Scale.</P>
<P>Upon this Tryal of it with Water the&s;e things are ob&s;ervable.</P>
<P N="1">1. That according to the proporti|on of the Elevation a&s;&s;igned to Water, it would have been &s;u&s;tained in a Tube of one and thirty foot high, and con&s;e|quently in this of eighteen Inches the Water had not attained a twentieth part of that height, at which it might in a Tube be kept &s;u&s;pended.</P>
<P N="2">2. That according to the&s;e mens Suppo&s;itions, the Su&s;pen&s;ion in the Tube, either of Water or Mercury, is &s;uppo&s;ed to be by the pre&s;&s;ure of a co|lumn of the Atmo&s;phere upon the Wa|ter or Mercury in the ve&s;&s;el, and there|by the column of Water or Mercury is
<PB N="168" REF="88">by that counterpoi&s;e driven up in the Tube. This Tube being but of eighteen Inches long, the forreign Atmo&s;pheri|cal pillar &s;till will urge the Water or Mercury to ri&s;e to an <HI>aequipondium</HI> with it, namely the Mercury to twenty nine Inches, the Water to thirty one foot, or thereabouts.</P>
<P N="3">3. And con&s;equently, according to their Suppo&s;ition, the Cylinder of Water, in the in&s;tance in que&s;tion, within the Tube, pre&s;&s;eth up the Tube, and would lift it up to one and thirty foot high, had the Tube been long e|nough.</P>
<P N="4">4. But as the Atmo&s;pherical Cylin|der without the Tube pre&s;&s;eth up the Water, &s;o the Atmo&s;pherical Cylinder incumbent upon the head of the Tube, pre&s;&s;eth it down; and &s;o according to tho&s;e men it is not the Waten in the Tube, that gives any counterpoi&s;e to the oppo&s;ite Scale, but the Atmo&s;phe|rical Cylinder, an&s;werable to the cavi|ty of the Tube, that pre&s;&s;eth upon the head of the Tube.</P>
<P N="5">5. And that weight of the Atmo|&s;pherical
<PB N="169" REF="88">Cylinder upon the head of the Tube, is counterpoi&s;ed by the forreign Cylinder, abating only &s;o much, as the proportion of the Water thru&s;t or kept up in the Tube, amounteth to; which being in the in&s;tance in hand about a twentieth part of what the forreign At|mo&s;pherical pillar weighs, the Atmo|&s;pherical pillar incumbent upon the head of the Tube weighs ju&s;t &s;o much as the Water included in the Tube a|mounts unto. But upon the whole mat|ter, this fine Theory appears to be but a hand&s;om Imagination. For it is plain, in the in&s;tance in hand, the At|mo&s;pherical Cylinder, incumbent upon the head of the Tube, is larger than the cavity of the Tube, and con&s;equently more weighty by far (if it have any weight at all) than that forreign Cylin|der of Atmo&s;phere, which is &s;uppo&s;ed to &s;u&s;tain the included column of Wa|ter, and the Tube it &s;elf is not &s;u&s;tained nor &s;u&s;tainable by the Water in the ve&s;|&s;el, but is wholly rai&s;ed by the weight in the oppo&s;ite Scale: and therefore the Suppo&s;ition, that the weight that pre&s;|&s;eth
<PB N="170" REF="89">upon the Scale, is the weight of the Cylinder of Air upon the Tube it &s;elf, is vain; for then it &s;hould &s;u&s;tain the weight, not only of the Tube, but another weight far greater than the forreign column of Air could counter|poi&s;e.</P>
<P>And that which &s;eems to me to con|vince this mi&s;take in the whole propo|&s;ed Theory, is this plain and obvious Experiment.</P>
<P><HI>Fig.</HI> 10. I therefore took a Gla&s;s-tube of about half an Inch diameter, 18 Inches long, clo&s;ed at one end; and weighing it exactly in the open Air, it weighed two Ounces and three quarters of an Ounce, and heating it very hot, where|by the included Air was highly rarified, I &s;u&s;pended the clo&s;ed end upon one Scale of a Ballance, and let the open end &s;ink a little into a ve&s;&s;el of Water, and counterpoi&s;ed it in the other Scale with two Ounces three quarters; and be|cau&s;e the end of the Tube did but little more than touch the Water, it held the &s;ame weight as before upon the Scale, <HI>viz.</HI> two Ounces three quarters.</P>
<PB N="171" REF="89">
<P>As &s;oon as the Tube was thus conti|guous to the Water, it attracted and rai|&s;ed the Water &s;o, that in half a quarter of an hour the Tube was filled twelve Inches with Water, the Air contracting in &s;elf to &s;ix Inches in the top of the Tube, whereby it appears it was rarified two thirds beyond its natural and or|dinary ri&s;e and &s;tandard, which now againe it acquired by contracting it &s;elf.</P>
<P>The Water which it attracted being carefully marked at its highe&s;t Elevati|on, and then &s;trictly mea&s;ured, weighed one Ounce and a quarter.</P>
<P>Now the things ob&s;ervable in this in&s;tance are the&s;e. 1. That the &s;ingle Tube, with the included rarified Air, did really weigh even in the external Air but two Ounces three quarters, and by that weight in the oppo&s;ite Scale it was perfectly kept <HI>in aequilibrio.</HI> 2. That when it touched the Superficies of the Water, and thereby attracted the Wa|ter into it, it pre&s;ently grew more weighty, which it gradually increa&s;ed, and accordingly more and more &s;ub&s;i|ded, Tube and all, into the &s;ubjected
<PB N="172" REF="90">ve&s;&s;el of Water, as it received into it more Water, and con&s;equently grew more weighty, 'till its full comple|ment of 12 Inches of Water drawn up into it 3. That when it was filled with twelve Inches of Water, then it weigh|ed the full weight of the Tube, and the Water <HI>viz.</HI> two Ounces three quar|ters for the weight of the Tube, and one Ounce and a quarter for the weight of the Water <HI>intato</HI> four Ounces, and therefore four Ounces in the oppo&s;ite Scale would keep it ju&s;t <HI>in aquibrio.</HI> On|ly care mu&s;t be taken, either by depre&s;|&s;ing the Water, or rai&s;ing the Ballance, that the Tube mu&s;t only touch the top of the Water, for otherwi&s;e the Water will run out, and prevent the tryal. Now to di&s;cover what it is that thus de|pre&s;&s;eth the Tube gradually, as the Water ri&s;eth up into the Tube, whe|ther the weight of the Tube, or the weight of the Water included in it, I will con&s;ider, 1. What the external column of Air, which tho&s;e Ma&s;ters &s;uppo&s;e to pre&s;s up the Water in the Tube, contri|butes
<PB N="173" REF="90">to it. and &s;urely according to this Suppo&s;ition of theirs, this is &s;o far from cau&s;ing any acce&s;s of Gravitation to the Tube or Water included in it, that it rather pre&s;&s;eth up the Tube, by pre&s;&s;ing and impelling the Water into it, and indeed it is that which they them&s;elves &s;ay, and build their Theories upon it, <HI>viz.</HI> that for this rea&s;on the Water in the Tube weighs nothing.</P>
<P N="2">2. What the column of Air impen|dent upon the top of the Tube, com|men&s;urate in diameter to the cavity of the Tube, doth contribute, which accor|ding to their Solution mu&s;t be it that weighs down the Tube by pre&s;&s;ing up|on it. But certainly this doth nothing in this ca&s;e; for if the Tube it &s;elf, filled with rarified Air, weighs in the open Air but two Ounces three quarters, it can never come to weigh four Ounces when in the Water, (where by rea&s;on of the thickne&s;s of the <HI>medium,</HI> it mu&s;t lo&s;e, and not gain weight,) and it had the &s;ame column of Air impendent upon its top, as well before its immer&s;ion in|to the Water, as after. And before its
<PB N="174" REF="91">immer&s;ion (whether it were full of com|mon Air, or of Air thus highly rarified by heat) it &s;till weighed neither more nor le&s;s than two Ounces three quar|ters.</P>
<P N="2">3. Therefore it remains, that it is the weight of the Water, that thus creeps up in the Tube, and in its a&s;cent to twelve Inches weighed ju&s;t one Ounce and a quarter that gravitates in the Tube, and renders the weight of the whole to be four Ounces, which in the oppo&s;ite Scale holds both Tube and Water <HI>in aeguilibrio.</HI></P>
<P>And as the Tube is &s;u&s;pended to the Ballance by the &s;tring or thrid, &s;o the included rarified Air is &s;u&s;pended to the top of the cavity of the Tube, by the powerful Laws of Nature, and lays hold upon the Superficies of the Water; and as it contracts it &s;elf more and more, draws up the column of Water higher and higher; as a Lute-&s;tring fa&s;tned to a fixed Body above, and to a &s;mall Weight below, after a high ten&s;ion rai&s;eth the Weight by contracting it &s;elf, and this to maintain the continuity of the parts of Nature.</P>
<PB N="175" REF="91">
<P>And this is a plain &s;en&s;ible and unfor|ced Solution; and it &s;eems to me, that tho&s;e that tell us, that it is only the Tube, and the incumbent Cylinder of Air only, that gives the weight, were impo&s;ed upon, though not by ignorance of Statical Laws, yet by fondne&s;s and partiality to a new invented <HI>hypothe&s;is.</HI></P>
<P N="2">2. The &s;econd In&s;tance that I &s;hall give, &s;hall be this: Take a Gla&s;s Tube, clo&s;ed at one end, of an Inch diameter in the cavity; fill it with Mercury, &s;top it with a &s;mall Engine, and invert it in|to a ve&s;&s;el of re&s;tagnant Mercury of an Inch and half diameter; then opening it by a contrivance which is not diffi|cult, after it is inverted in the Mercury, the Mercury will be &s;u&s;tained at twenty nine Inches and half, as well as if the ve&s;&s;el of re&s;tagnant Mercury were of &s;ix Inches diameter.</P>
<P>And yet it is apparent, that the rim or round Superficies of the ve&s;&s;el of re|&s;tagnant Mercury, is not above one fourth part in <HI>area</HI> of the Mercurial Cy|linder, and cannot be pre&s;&s;ed with a co|lumn of Air commen&s;urate to the cavi|ty
<PB N="176" REF="92">of the Tube; for the incircling co|lumn of Mercury is not a fourth part of the <HI>area</HI> of the Tube, neither can it be pre&s;&s;ed with a column of Air of a grea|ter diameter or dimen&s;ion than that lit|tle rim of Mercury that incompa&s;&s;eth the Tube. So that it is not the <HI>aequipon|dium</HI> of the Atmo&s;pherical Column that &s;u&s;tains the Mercury in the Tube, for if it &s;hould; a column of Air of the fourth part of an Inch diameter, &s;hould be as weighty as a column of Air of an Inch diameter, becau&s;e it mu&s;t in this In&s;tance make an <HI>aequipondium</HI> to a weight of Mercury, commen&s;urate to a column of Air of an Inch diameter.</P>
<P>Therefore it is not the <HI>aequipondium</HI> of the Air that &s;u&s;tains the Mercury in the Tube, but &s;omething el&s;e, and what that is, we &s;hall here after examine.</P>
<P N="3">3. My third In&s;tance is that com|mon one: If the <HI>Torricellian</HI> Engine be put in practice, in a great Gla&s;s Recei|ver, wholly excluding any communi|cation with the forreign Air, the Mer|cury will be &s;u&s;pended at twenty nine Inches and half, as well as in the free
<PB N="177" REF="92">Air. And yet here can be no Atomo|&s;pherical column, reaching from the top of the Atmo&s;phere to the re&s;tagnant Mercury, with its Gravitation, to &s;u|&s;tain the Mercurial column, the &s;ame being intercepted and broken by the in|terpo&s;ition of the Gla&s;s.</P>
<P>And this plain obvious evident In|&s;tance had wholly de&s;troyed the <HI>hypothe|&s;is,</HI> and utterly di&s;ordered and &s;cattered all the <HI>pori&s;mata</HI> and Con&s;equences built upon it, had not another &s;upple|mental invention &s;tept in to relieve it, namely the prodigious Elatery of the free Air, which upon a due examinati|on will prove as great a mi&s;take, and as impotent to relieve this deficient <HI>hypo|the&s;is</HI> as the former; and if it prove &s;o, I doubt our new Philo&s;ophers mu&s;t be fain to return to the <HI>decantata fuga vacui</HI> for a better Solution.</P>
</DIV2>
<DIV2 N="12" TYPE="chapter">
<PB N="178" REF="93">
<HEAD>CHAP. XII.</HEAD>
<HEAD TYPE="sub"><HI>Touching the Elatery or Spring of the Air.</HI></HEAD>
<P>I Come now to con&s;ider that &s;ub&s;idi|ary help, &s;ub&s;tituted by the New Philo&s;ophy, for the Solution of the <HI>Phaenomena</HI> of the <HI>Torricellian</HI> and o|ther Experiments of this nature: and herein I &s;hall con&s;ider the&s;e things.</P>
<P N="1">1. What Elatery or Spring is of all hands agreed to be truly found in the Air.</P>
<P N="2">2. What Elatery or Spring is &s;ub&s;titu|ted by the late Philo&s;ophy, and how ap|plied by them to the Solution of <HI>phaeno|mena</HI> of this kind.</P>
<P N="3">3. The Arguments, Rea&s;ons, and Evi|dences that evince the mi&s;take of this new Elaterical Suppo&s;ition.</P>
<P>Fir&s;t, as to the former of the&s;e, this is agreed of all hands, that the Air being a &s;ubtle Fluid, is capable of an acciden|tal Ela&s;ticity of very great efficacy and force: namely, when by accidental im|pre&s;&s;ion
<PB N="179" REF="93">upon it, it lo&s;eth that common and natural &s;tate or con&s;i&s;tence, that otherwi&s;e belongs to it.</P>
<P>As I. by a great compre&s;&s;ion of its parts together, &s;uch as we &s;ee in Wind|guns, whereby it is compre&s;&s;ed into a &s;pace &s;ometimes &s;even times le&s;s than that which is natural to it, and then by a natural and &s;trange motion of re&s;titu|tion it hath an Ela&s;ticity, whereby to regain its natural &s;tate and po&s;ition. 2. By con&s;tipation of its parts by Cold, whereby it is bound up &s;ometimes to a narrower room, and then by the ap|proach of convenient heat, that con&s;ti|pation is relaxed, and the Air regains its natural liberty, motion, and con&s;i|&s;tency: and 3. by Rarifaction by heat, whereby it is expanded beyond its na|tural &s;ize, and as it grows cold, it obtains a kind of Ela&s;ticity in ward, and an in|ward endeavouring to contract it &s;elf to its natural &s;ize and dimen&s;ion. 4. In a &s;trong ten&s;ion by an accidental or col|lateral force, whereupon it con|tracts it &s;elf as much as it can to its na|tural &s;tate, and re&s;i&s;ts that ten&s;ion
<PB N="180" REF="94">which di&s;compo&s;eth and extends it; from whence follows that which is u&s;ually called Suction, or Attraction, of which I &s;hall have occa&s;ion hereafter to write more at large.</P>
<P>Again 2. it mu&s;t be agreed, that al|though the Air in its natural con&s;i|&s;tence is by a great force compre&s;&s;ible into a clo&s;e order, yet it doth re&s;i&s;t &s;uch a compre&s;&s;ion, and doth not ea&s;ily yeild to it; and therefore take a Tube of any con&s;iderable length, clo&s;ed at one end, and the open end inverted upon the Water, and pre&s;&s;ed down, yet the Air included will retain very much of its natural &s;tate, and receives but a &s;mall contraction by the counterpre&s;&s;ure of the Water, po&s;&s;ibly an Inch in two or three, or &s;omewhat more, according to the depth of its immer&s;ion.</P>
<P>But the&s;e Elateries are not &s;uch as concern the pre&s;ent que&s;tion.</P>
<P>Therefore I come to the Suppo&s;ition of the new Philo&s;ophy, in relation to this bu&s;ine&s;s of Ela&s;ticity of the Air, which the attribute to the common and free Air in which we breath and
<PB N="181" REF="94">live; and if I mi&s;take them not, their Suppo&s;ition is this: I. That the Air is a kind of Spungy Body, not much unlike (as to this pur|po&s;e) to a Spunge or Fleece of Wool, capable of compre&s;&s;ion, and under that compre&s;&s;ion endeavouring to loo&s;en and di&s;charge it &s;elf by that which we call Springine&s;s or Ela&s;ticity.</P>
<P>And herein we do not con&s;iderably differ, only they &s;ay that this Ela&s;ticity is of a va&s;t, and almo&s;t unlimited nature, that &s;carce hath any bounds to it; we &s;ay that it hath more contracted and de|termined limits of its Ela&s;ticity, and tho&s;e are &s;uch as every portion of free Air obtains in a common and u&s;ual &s;tate of the temperament of the Weather.</P>
<P N="2">2. Again they &s;ay, that the Body of the Air, or at lea&s;t of the Atmo&s;phere, con&s;i&s;ts of a great many little crooked filaments like Springes, which when extended to a greater &s;traightne&s;s than is &s;uitable to them, as in its high ten&s;ion or rarifaction, indeavour regaining of their natural curvitude; and when by any weight or force they are drawn clo&s;e to|gether,
<PB N="182" REF="95">they, &s;pring out to their ju&s;t ex|ten&s;ion, and that gives a common Springine&s;s to the Air in &s;uch a con&s;i|&s;tence or circum&s;tance.</P>
<P N="3">3. That the &s;uperior parts of the Air gradually gravitate and compre&s;s the inferior parts, and therefore the higher the Atmo&s;phere or Air is, the le&s;s it is compre&s;&s;ed, but the lower it is, the more it is compre&s;&s;ed, the lower|mo&s;t parts receiving and &s;u&s;taining the pre&s;&s;ure of all the&s;e parts that are above.</P>
<P N="4">4. That the actual Elatery, or Spring of the Atmo&s;phere, or Air, is the i&s;&s;ue or effect of this Gravitation; and the more the Gravitation is, the greater the Spring of tho&s;e parts are, when they can but get liberty to expand them&s;elves; for the greater weight doth the more bind and incurvate the&s;e crooked filaments, which makes them fly out extremely, when they can get them&s;elves unfettered from the oppre&s;|&s;ing weight, and even while they are under that pre&s;&s;ure they have their <HI>cona|<GAP DESC="illegible" EXTENT="1 letter">us</HI> for their liberty.</P>
<P N="5">5. That becau&s;e the lower parts of
<PB N="183" REF="95">the Air next the Earth are mo&s;t pre&s;&s;ed upon by the &s;uperior parts, therefore the lower parts of the Air have the grea|te&s;t Ela&s;ticity and Springine&s;s, which it exerci&s;eth according as it gets liberty.</P>
<P N="6">6. That therefore this inferior Air hath a natural va&s;t propen&s;ion to Ex|ten&s;ion, and amplifying of it &s;elf, in&s;o|much that if we &s;hould &s;uppo&s;e any part of the Univer&s;e were free from any Bo|dy, or had a more &s;ubtle Body than that of the common Air, if a portion of the lower Air next the Earth were placed there, it would upon the account of its own natural Ela&s;ticity, expand it &s;elf as largely, and it may be much larger than tho&s;e Artificial Expan&s;ions wrought by fire in <HI>AEolipiles,</HI> and other Engines, wherein neverthele&s;s the Air may be &s;o ordered, as to po&s;&s;e&s;s &s;eventy times more room than before it had.</P>
<P N="7">7. That therefore when we &s;ee a little portion of Air included in a Tube, in the <HI>Torricellian</HI> Experiment, exten|ded upon the de&s;cent of the Mercury four, five, or &s;ix Inches, or into a larger room than it po&s;&s;e&s;&s;ed upon its fir&s;t in|clu&s;ion
<PB N="184" REF="96">this is no forced ten&s;ion of the Air, but a free natural expan&s;ion of it &s;elf, having gained room and opportu|nity, by the de&s;cent of the Mercury, for its recception; and therefore this natu|ral expan&s;ion of that included particle of Air, is one great help towards the de|&s;cent of the Mercury, 'till it comes to its &s;tation.</P>
<P N="8">8. That in as much as the Ela&s;tici|ty of the Air, when contiguous to the Earth, or other &s;olid Body, is impeded in its Ela&s;ticity downward by the re&s;i|&s;tance of the Earth, it is as it were re|verberated upward, and laterally, where it may be exerci&s;ed: which is a great means of that &s;upport that the recoiling Aereal particles give to weighty Bodies, which is &s;een in the &s;u&s;tentation of the lower of the adhering Marbles.</P>
<P N="9">9. That every part of the lower Air is under the &s;ame compre&s;&s;ion with the &s;ame region wherein it is, and therefore if a portion of the free or open Air be inclo&s;ed within a Gla&s;s-Receiver, clo&s;ed on every &s;ide, yet it hath the &s;ame Ela|&s;ticity that the portion of Air had, out of which it was taken.</P>
<PB N="185" REF="96">
<P N="10">10. And becau&s;e that Airin the Gla&s;s is on every &s;ide penned up, and its Ela|&s;ticity being as it were reverberated from every &s;ide of the Gla&s;s, doth the more inten&s;ely and forcibly recoil in|ward: and therefore it comes to pa&s;s, that though the great Gla&s;s Receiver, compa&s;&s;ing in the <HI>Torricellian</HI> Engine on every &s;ide, be de&s;titute of the weight of the column of Atmo&s;phere, to &s;u&s;|pend the Mercury by its <HI>aequipondium;</HI> yet the included Air doth the very &s;ame thing by its Elatery or Spring upon the re&s;tagnant Mercury.</P>
<P>And thus we &s;ee how, for the accom|modating of the <HI>Torricellian phaeno|nomena,</HI> and &s;ome others of like nature, where the <HI>pondus Atmo&s;phoericum</HI> cannot be had nor acquired, what a laborious invention and proce&s;s is framed for the &s;upply of that deficiency.</P>
<P>Therefore I come to con&s;iderand ex|amine, whether this laborious proce&s;s have any thing of truth and reality in it, or whether, as that of the <HI>pondus cylin|dri Atmo&s;pharici,</HI> it be only a fine in|vention to help and &s;upport a lame and
<PB N="186" REF="97">langui&s;hing <HI>hypothe&s;is</HI> or Solutions.</P>
<P>Although what&s;oever doth oppo&s;e the Gravitation of the commen Air, doth as nece&s;&s;arily conclude again&s;t this Ela&s;ticity of the free and common Air; and although much of what I have written in the third and tenth Chap|ters, again&s;t the Gravithtion of the Air, is equally applicable again&s;t this imagi|nary Ela&s;ticity thereof, &s;ince the Ela|&s;ticity is by the <HI>hypothe&s;is</HI> &s;uppo&s;ed to be the effect of its Gravitation; yet I &s;hall repete nothing, or very little, of what I have there &s;aid, but apply my &s;elf &s;ingly to the di&s;cu&s;&s;ion of this Elatery or Sprin|gine&s;s of the common or free Air, both by Rea&s;on and by Experiments.</P>
<P N="1">1. The Spring of the Air is bottom|ed upon the &s;uppo&s;ition of the actual pre&s;&s;ure of the &s;uperior parts of the Air or Atmo&s;phere upon the inferior, and the lower parts being under the grea|ter pre&s;&s;ure, hath con&s;equently the grea|ter Elatery. But upon what hath been before &s;aid, in the third Chapter, there is no &s;uch Gravitation or pre&s;&s;ure of the Air or Atmo&s;phere, and con&s;equently
<PB N="187" REF="97">no &s;uch Elatery in the free and open Air.</P>
<P N="2">2. If there &s;hould be admitted any &s;uch Ela&s;ticity in a portion of the Air below in this inferior region, included within a Gla&s;s ve&s;&s;el or Receiver, (the in&s;tance for who&s;e &s;ake this invention was principally devi&s;ed,) &s;o as to &s;u&s;tain the &s;u&s;pended column of Mercury, then of nece&s;&s;ity there mu&s;t be the &s;ame Ela|&s;ticity of the &s;ame or the like portion of the common Air, (for it is all &s;uppo&s;ed under the &s;ame common pre&s;&s;ure of the &s;uperior parts:) the con&s;equence where of mu&s;t needs be, that either the attri|bution of that Su&s;pen&s;ion to the Gravi|tation of a Column of the Air, and all the delicate Con&s;ectaries thereupon, are more Fancies and Mi&s;takes, becau&s;e the whole <HI>phaenomenon</HI> is performable and performed by the Ela&s;ticity of the Air, as well without as within this clo&s;e Gla&s;s ve&s;&s;el; or el&s;e the joint power of the <HI>pondus,</HI> as well as the Ela&s;ticity of the forreign Air, mu&s;t rai&s;e the Mercu|ry in the Tube to fifty nine Inches, &s;ince the Elarery of the Air alone, without
<PB N="188" REF="98">the aid of the Gravity of the Atmo&s;phe|rical Cylinder in the inclo&s;ed ve&s;&s;el, is able to keep it &s;u&s;pended to twenty nine Inches and half. But we &s;ee the con|trary in the Experiment tried, as well within as without the inclo&s;ed Gla&s;s; therefore either the weight of the At|mo&s;pherical Cylinder, or its Elatery, mu&s;t be laid a&s;ide in this Solution, or, which is the truer Conclu&s;ion, neither the one nor the other are to be admitted, but both are to be rejected as cro&s;&s;ing one another, and al&s;o the truth of the Solution.</P>
<P N="3">3. Nay, but yet farther, if this Ela|tery be admitted, the whole Scheme of the Gravitation of the Air, or any part thereof, mu&s;t be rejected as fictitious, and impo&s;&s;ible; and on the other &s;ide, if the &s;uppo&s;ed Gravitation of the Air or At|mo&s;pherical Cylinder be admitted, the Elatery mu&s;t be rejected, and the whole Air will be <HI>in aequilibrio,</HI> in as much as upon this &s;uppo&s;ition of this New Phi|lo&s;ophy, the Elatery pre&s;&s;eth as much upward, as the Gravitation doth down|ward, and <HI>&egrave; conver&s;o</HI> the Gravitation as
<PB N="189" REF="98">much downward, as the Elatery doth upward: &s;o that after all this laborious <HI>apparatus</HI> of Gravitation, and Cylinders, and Atmo&s;phere, and Elatery, the Air is at quiet, at re&s;t, and <HI>in aequilibrio,</HI> which is ea&s;ily granted without all this difficult <HI>hypothe&s;is.</HI></P>
<P>For according to the&s;e mens &s;uppo&s;i|tion (if we &s;hould admit it) the Atmo|&s;phere were &s;even Miles high, we mu&s;t needs &s;uppo&s;e that the greate&s;t Elatery is next the Superficies of the Earth, be|cau&s;e there it is more charged with the weight of the &s;uperior parts of the Air; and becau&s;e the rerre&s;trial Globe checks the Elatery of it downward; the Elatery mu&s;t di&s;charge it &s;elf by its motion up|ward, and &s;o encounter the pre&s;&s;ure of the Air, by how much more its Springs and crooked Particles are charged. And a Mile higher in the Atmo&s;phere where is le&s;s pre&s;&s;ure, there is con&s;equently le&s;s Elatery or re&s;i&s;tance of that pre&s;&s;ure, and yet &s;ufficient to keep that rundle of Atmo&s;phere in an <HI>aequilibrium.</HI></P>
<P>And it is plain, that this Connter|motion of the &s;uppo&s;ed Spring, or Ela|tery,
<PB N="190" REF="99">and Gravitation of the Air, mu&s;t by their mutual conflict, one cheok and refract the other.</P>
<P>But then it is hoped, that the interpo|&s;ition of another gro&s;s Body between the ponderous Air tending downward, and the reverberated, recoiling, Ela&s;ti|cal Air tending upward, may part the fray; and thereupon in the in&s;tance of the two cohering Marbles, the upper column of impending Air may pre&s;s down the upper Marble, and the lower column of recoiling Air may pre&s;s up the lower Marble.</P>
<P>But this will do nothing to help the bu&s;ine&s;s in hand, touching the Mercu|rial column in the <HI>Torricellian</HI> Experi|ment (for as for the cohe&s;ion of the two Marbles, and the rea&s;on of it, I &s;hall in its due place examine.)</P>
<P>For it is plain there, that if there be any Ela&s;ticity in the Air next the Earth, there is proportion for proportion as much Ela&s;ticity in the Air next the re|&s;tagnant Mercury, upon which it is in|cumbent, and which we may if we plea&s;e, place even to the Superficies of
<PB N="191" REF="99">the Earth; for the column of Air (<HI>ex &s;uppo&s;itione</HI>) proportionable in ba&s;e to the Mercury, is as really gravitating upon the Mercury, as upon the Earth, and con&s;equently there is the very &s;ame Ela|tery or <HI>&s;ur&s;um</HI> pre&s;&s;ure of inferior parts of that Atmo&s;pherical pillar incumbent upon the Mercury, that would break the Gravitation of that upper Atmo|&s;pherical Cylinder, and render it inef|fectual.</P>
<P>Be&s;ides all this, as it requires a &s;trong Phanta&s;y to &s;uppo&s;e this wonderful Ela|&s;ticity of the Air, &s;o it requires a much more potent phanta&s;y to keep the Ela|&s;ticity of it within the preci&s;e lateral di|men&s;ions of the Atmo&s;pherical pillar in a &s;traight line: for the Ela&s;tical par|ticles of the Aereal parts, adjacent to that Atmo&s;pherical Cylinder, will in|croach and break it upon this Cylinder, and di&s;order and refract its pre&s;&s;ure, be|&s;ides what the concu&s;&s;ion of Winds would effect.</P>
<P N="4">4. But &s;uppo&s;e in the free Air the <HI>pondus deprimens</HI> of the Atmo&s;pherical Cylinder were too hard for its Elatery,
<PB N="190" REF="100">&s;o although in an inclo&s;ed Gla&s;s the Ela|tery doth the whole bu&s;ine&s;s in &s;u&s;pen|ding the Mercury in the Tube, yet in the open Air the <HI>pondus deprimens</HI> con|quers its Ela&s;ticity, and the whole <HI>phae|nomenon</HI> &s;hall be there performed by the <HI>pondus deprimens</HI> of the aereal Cylinder: I &s;ay &s;uch a Suppo&s;ition as this would render the lower parts of the Air unmo|veable, and bind it up &s;o, that it could never &s;tir without an admirable relaxa|tion of it by the violence of heat, which is contrary to all the experience of the World. For we &s;ee by the &s;malle&s;t winds the motion of Smoak, and a thou|&s;and In&s;tances more, the lower parts of the Air are in a perpetual flux and motion, which it could never do, if un|der &s;o rigorous a con&s;tipation and com|pre&s;&s;ion by its &s;uperior parts. And though this immediately contradicts the great pre&s;&s;ure of the inferior Air by the &s;uperior, yet by nece&s;&s;ary con&s;e|quence it contradicts the &s;uppo&s;ed Ela|tery thereof.</P>
<P N="5">5. But as to the very in&s;tance before given, of the &s;u&s;pen&s;ion of the Mercury
<PB N="193" REF="100">in a Tube placed in a clo&s;ed Gla&s;s Re|ceiver, protected from the impendent aereal ponderous Cylinder; I &s;ay, that the &s;u&s;pen&s;ion of the Mercury is not cau&s;ed either by the Weight or the Ela|tery of the Air. Not by its weight, be|cau&s;e the Atmo&s;pherical column is in|tercepted, and kept off by the interpo&s;i|tion of the Gla&s;s; it remains therefore that it mu&s;t be done by the Elatery or Spring of the Air included in the ve&s;&s;el: but that cannot po&s;&s;ibly do it, for the&s;e Rea&s;ons. 1. Becau&s;e that Elatery that mu&s;t &s;u&s;tain the column of Mercury, cannot be an Elatery pre&s;&s;ing upward or laterally, but it mu&s;t be &s;uch an Ela|tery as mu&s;t pre&s;s downward, to bear again&s;t the excur&s;ion of the &s;u&s;pended column of Mercury, and thereby keep it <HI>in aequilibrio:</HI> and certainly if there be any Elatery of the Air, it mu&s;t bear ra|ther upward again&s;t what pre&s;&s;eth it down, and cau&s;eth it, than downward. 2. But if it be &s;aid that by the Receiver, or Gla&s;s inclo&s;ing the Air every way, the Elatery is as well turned downward as upward, and &s;o counterpoi&s;eth the co|lumn
<PB N="194" REF="101">of Mercury, and &s;o it is not like the recoil of the Spring of the Air from the Earth, which mu&s;t be principally upward, becau&s;e checked and reverbe|rated at its ba&s;e; but here the reper|cu&s;&s;ion is from all parts of the Gla&s;s, as well from above as beneath. I &s;ay this very objection renders it utterly impo&s;|&s;ible, that the Elatery of the Air in the Gla&s;s can cau&s;e this Su&s;pen&s;ion, or in any mea&s;ure contribute to it. For let us &s;uppo&s;e the Gla&s;s Receiver to be &s;pheri|cal, the repercu&s;&s;ion of the Elatery of the Air mu&s;t be equal from all parts: the con&s;equence whereof mu&s;t nece&s;&s;a|rily be, than this Elatery pre&s;&s;eth as well upwards as downward, and from every part of the Spherical cavity of the Gla&s;s, the con&s;equence whereof mu&s;t needs be, that the whole Elatery is in &s;u&s;pence, and one Ela&s;tical line breaks, refracts, and retunds, another; &s;o that the tendency of this Ela&s;ticity is neither upwards nor downwards, not from any point of the Compa&s;s, but all things are at re&s;t, as where Winds blow with an equal &s;trength every way, the
<PB N="195" REF="101">Air is undi&s;turbed, and &s;o no pre&s;&s;ure at all made upon the Mercury, but it is but a meer eva&s;ion to &s;hore up an <HI>hypo|the&s;is.</HI></P>
</DIV2>
<DIV2 N="13" TYPE="chapter">
<HEAD>CHAP. XIII.</HEAD>
<HEAD TYPE="sub"><HI>Certain Experiments, evincing that the common Air in its ordinary con&s;i&s;tence, hath no, or no con&s;iderable. Ela&s;ticity or Spring, without an accidental or preter|natural Compre&s;&s;ion.</HI></HEAD>
<P>IN the former Chapter I have given the rea&s;ons again&s;t the wonderful Ela&s;ticity of the Air, or Atmo&s;phere, and the in&s;ufficiency of that Suppo&s;iti|on to give a Solution to the <HI>phaenomena</HI> in the <HI>Torricellian</HI> Experiment. And I now come to &s;ome experimental In&s;tan|ces, farther illu&s;trating and proving what I have &s;aid in the former Chap|ter, namely that either there is no Ela|&s;ticity at all in the common Air, nor in any part thereof inclo&s;ed in the ve&s;&s;el, <HI>de quo &s;upra,</HI> or if any at all, yet very lit|tle,
<PB N="196" REF="102">and &s;uch as is no ways able to keep &s;uch a column of Mercury &s;u&s;pen|ded, which may po&s;&s;ibly weigh ac|cording to the amplitude of the Tube two or three pounds, which yet we &s;ee &s;u&s;pended in the <HI>Torricellian</HI> Ex|periment.</P>
<P>For it is a certain and demon&s;trable truth, that if any <HI>potentia,</HI> be it what it will, &s;u&s;tains a weight or <HI>pondus depri|mens,</HI> the <HI>potentia &s;u&s;tentans</HI> mu&s;t be of an equal &s;trength to that weight, o|therwi&s;e it mu&s;t give way, and yeild to it.</P>
<P>Therefore if the <HI>potentia</HI> of the Ela|&s;ticity of the common Air (not compre&s;|&s;ed or con&s;tipated accidentally) be not equal in this in&s;tance to two pound of Mercury, it can never &s;u&s;tain or keep it &s;u&s;pended: and this is that which I &s;hall endeavour to make good.</P>
<P><HI>Fig.</HI> 12. Take a Bottle-Gla&s;s <HI>A,</HI> fill it with Water to <HI>B,</HI> which may contain about &s;ix Ounces of Water, the re&s;t of the Bottle full of Air; then take the Bolts-head <HI>C,</HI> heat it very hot, that the Air may be in a great mea&s;ure driven
<PB N="197" REF="102">out of it, and the re&s;t highly rarified and expanded: Invert it into the Gla&s;s Bottle, &s;o that the free Air may come in, (though but at a Pin-hole,) as the Air in the Bolts-head grows cool, and con|&s;equently contracted neer to its natural &s;ize and &s;tate: the Air thus rarified, the Water in the Bottle will be drawn up into the Bolts-head to &s;upply the va|cancy, which otherwi&s;e would happen by the re&s;titution of the Air. But if the fi&s;&s;ure between the Bottle and Shank of the Bolts-head had been ha&s;tily &s;o clo|&s;ed, that no Air could enter into it, &s;ome Water would ari&s;e as &s;uppo&s;e to <HI>D,</HI> but the whole Water would never be driven up out of the Bottle by any Elatery of the Air included in it; but only the &s;u|perior Air in <HI>C,</HI> being &s;o highly rarified by the heat, that one third part of the Air in <HI>C,</HI> as it &s;tood unrarified, takes up the whole Bolts-head by rarifaction; and as the Air in the Bolts-head grows to its natural temper, and con&s;equently endeavours to retract it &s;elf to its natu|ral dimen&s;ion, &s;o having the fluid Wa|ter to work upon, it draws it up, and by
<PB N="198" REF="103">the advantage of that attraction gives a ten&s;ion or expan&s;ion to the Air in the upper part of the Bottle, as much as is capable to be obtained by the &s;trength of the attraction and &s;uction of the rari|fied Air in the Bolts-head, which draw|ing up the Water, and leaving le&s;s Wa|ter there than before, mu&s;t needs expand the inclo&s;ed Air in the top of the Bottle, to &s;upply that rece&s;s.</P>
<P>Now if the Air in the head of the Bottle, being taken out of the common Air, and of the &s;ame con&s;i&s;tence with it, had that &s;trong Elatery that the&s;e men &s;uppo&s;e, &s;o that it reacheth as it were after a dimen&s;ion five, nay forty times larger than that it hath, it would thru&s;t up the whole Water in the Bot|tle as high as <HI>E,</HI> as it would have done if the fi&s;&s;ure between the Bolts-head and the Bottle had not been &s;trictly clo&s;ed.</P>
<P>And this it &s;hould have done the ra|ther, becau&s;e the &s;uperior Air is &s;o much rarified, that it takes up three times the room of common unexpanded Air, and &s;o is capable of a more effectual impre&s;|&s;ion from the Air in the Bottle, and
<PB N="199" REF="103">would not re&s;t at <HI>D,</HI> but drive up the Water as high as <HI>E.</HI></P>
<P>And if any &s;hall &s;ay, that the weight of the interpo&s;ed Water is too great for its Elatery, to thru&s;t it up as high as <HI>E;</HI> certainly he that &s;hall &s;uppo&s;e that the Elatery of the Air, included in a clo&s;e Receiver, is able to thru&s;t and keep a column of Mercury to twenty nine Inches high, which column weighs po&s;|&s;ibly a pound or more, cannot doubt but the Elatery of the Air in the top of the Bottle, if it were of that force that the&s;e men &s;uppo&s;e, would thru&s;t up five or &s;ix Ounces of Water, about five or &s;ix Inches high, into the Bolts head.</P>
<P>But the plain truth is, that in this in|&s;tance, nor any of the like nature, it is neither the weight nor the Elatery of the Air included in the Bottle, that for|ceth up any drop of Water above its Superficies, but the powerful attraction of the expanded Air in the Bolts-head, endeavouring its own contraction when growing cold, and &s;o attracting the Water to &s;upply that <HI>ca&s;ma,</HI> that would otherwi&s;e follow upon its attraction.</P>
<PB N="200" REF="104">
<P>And therefore when by the de&s;cent of the Mercury a little portion of Air in the top of the Tube in the <HI>Torricellian</HI> Engin, gains four or five times a greater extent than it had before; this is done by the ten&s;ion of that little aereal Cylin|der, by the force of the de&s;cent of the Mercury, as &s;hall be more at large &s;hewn hereafter, and not as is groundle&s;ly &s;up|po&s;ed by the natural Ela&s;ticity or expan|&s;ion of that portion of Air. For if that &s;hould be the cau&s;e, it were nece&s;&s;ary that the finger &s;topping the top of the inverted Tube open at both ends, &s;hould be thru&s;t up, and not drawn in, and an empty Bladder &s;hould be more compre&s;|&s;ed than di&s;tended by &s;uch Ela&s;ticity of the included Air, the contrary whereof is evident both to Sen&s;e and Experience.</P>
</DIV2>
<DIV2 N="14" TYPE="chapter">
<PB N="201" REF="104">
<HEAD>CHAP. XIV.</HEAD>
<HEAD TYPE="sub"><HI>The con&s;ideration of &s;ome Arguments for the weight and Elatery of the Air.</HI></HEAD>
<P>I Shall not &s;pend much time upon The&s;e arguments, but only note &s;ome general Ob&s;ervations upon them, and then &s;ingle out &s;ome In&s;tances wherein I &s;hall be more particular.</P>
<P>In general therefore I &s;ay, 1. That all tho&s;e In&s;tances and Ex|periments produced to prove &s;uch a Weight or Ela&s;ticity of the free Air, that may be capable of effecting the <HI>phaenome|na</HI> in the <HI>Torricellian</HI> Experiment, yea or in the <HI>Magdeburgh</HI> In&s;trument, or the <HI>Engli&s;h</HI> Air-pump, are all capable of ano|ther Solution, as appears by the an|&s;wers that <HI>Linus</HI> hath given to them, which I need not repeat.</P>
<P N="2">2. That the application of the Weight and Ela&s;ticity of the Air to the Solution of the&s;e <HI>phaenomena,</HI> is forced, &s;treined, and in many in&s;tances contra|ry
<PB N="202" REF="105">to the evidence of Sen&s;e; &s;o that though the appearances them&s;elves are true, yet tho&s;e Cau&s;es a&s;&s;igned are very inevident, full of difficulties and ab&s;ur|dities, and require &s;uch a train of &s;upple|mental Suppo&s;itions to make them but Tolerably applicable, that no man di&s;|ingaged from a party can ea&s;ily &s;ub&s;cribe to them.</P>
<P N="3">3. That there are &s;ome In&s;tances and Experiments that are &s;o untractable to this method of Solution, that all the inventions of the mo&s;t Mercurial wits and highe&s;t ingaged in the patronage thereof, cannot by any means relieve it.</P>
<P N="4">4. That the plain and common So|lution of them by the in&s;eparability of Bodies, and the <HI>fuga vacui,</HI> (plea&s;antly by &s;ome &s;tiled <HI>decantata olim fuga vacui</HI>) doth mo&s;t naturally, and without any &s;tre&s;s offered to Sen&s;e or Nature, an&s;wer all In&s;tances and difficulties, and fails in none.</P>
<P N="5">5. That it is mo&s;t evident to any man, that without prejudice or partiali|ty &s;hall ob&s;erve it, all or the mo&s;t part of tho&s;e In&s;tances and Experiments,
<PB N="203" REF="105">which (to &s;erve the <HI>hypothe&s;is</HI> of the gra|vitation and Ela&s;ticity of the common Air) are re&s;olved into Pre&s;&s;ion or Ela|&s;ticity of the Air, are plainly performed by Suction and Attraction of the Air, when put under a great ten&s;ion or rari|faction, which wholly &s;ubverts the So|lution by Pre&s;&s;ure or Ela&s;ticity of the Air.</P>
<P>Now as to &s;ome particular In&s;tances.</P>
<P>Fir&s;t, we are told that the <HI>Torricellian</HI> Engin, wherein at the bot<GAP DESC="illegible" EXTENT="3 letters"> of the hill, the Mercury ri&s;eth to twenty nine Inches and half, carried up to the top of the hill <HI>Puy de dome</HI> in <HI>France,</HI> &s;ub&s;ided three Inches: and &s;ome In&s;tances of like nature given in <HI>Lanca&s;hire,</HI> it &s;ub|&s;ides neer two Inches. From whence it is inferred, that this variation ari&s;eth, becau&s;e upon the top of the Mountain, which was 3000 foot high, the column of the Atmo&s;phere was &s;horter, and &s;o gravitated le&s;s upon the re&s;tagnant Mer|cury, than it did at the bottom of the hill, which cau&s;ed the di&s;parity of the po&s;ition.</P>
<P>I an&s;wer, admitting the fact true, yet
<PB N="204" REF="106">the cau&s;e a&s;&s;igned is <HI>non cau&s;a pro cau&s;a,</HI> or at lea&s;t we have no &s;ufficient evidence that this is the cau&s;e.</P>
<P>The various Elevation or depre&s;&s;ion of the Mercury is not in re&s;pect of the height or lowne&s;s of the place, where the In&s;trument is u&s;ed, but in re&s;pect of the temperamont of the Air wherein it is u&s;ed. The Excellent Author tells us, in his eighteenth Experiment, that the <HI>Torricellian</HI> Engin placed in his Chamb<GAP DESC="illegible" EXTENT="2 letters"> window for a good &s;ea&s;on, the Mercury had various Elevations and &s;ub&s;idings, according to the temper of the Air; and that this variation was con&s;iderable, namely two Inches, and that in cold weather, contrary to the u&s;e of other Weather-Gla&s;&s;es, it fell much lower than at other times. And if this be&s;o, it is no wonder, at the top of the hill, where the Air was much colder, it might &s;ub&s;ide con&s;iderably from the height it had at the bottom.</P>
<P>But whether it were colder or hot|ter, yet certainly there is that difference of temperament in the various regions of the Air, that might make a various
<PB N="205" REF="106">po&s;ition in the Mercury. What if we &s;hould &s;ay, that the <HI>vis igneapenetrativa AEtheris</HI> is &s;tronger there than below the hill, and &s;o might &s;trongly dilate that &s;mall portion of Air upon the top of the hill, though the &s;en&s;e of heat be there le&s;s?</P>
<P>But I cannot chu&s;e but ob&s;erve, that if we &s;hould a&s;&s;ign this Sub&s;idency of three Inches of Mercury to the &s;hortning of the Atmo&s;pherical Cylinder, by 500 Fathoms of perpendicular height; we mu&s;t nece&s;&s;arily conclude the great mi|&s;takes in the computation of the gravi|table Air or Atmo&s;phere, and mu&s;t ren|der it of a prodigious height beyond all the E&s;timates of the latter Elateri&s;ts, whereof &s;ome tell us it is &s;even Miles high. By others Computation that it is 33893 Feet, which is 5648 Fa|thoms, &s;omewhat le&s;s than &s;even Miles.</P>
<P>But if a Mile next the Earth &s;hould abate but three Inches in the height of the Mercury, &s;ix Miles more would hardly abate three Inches more, <HI>viz.</HI> &s;ix Inches; nor twenty four Miles more
<PB N="206" REF="107">would abate nine Inches. For a Mile of Air next the Earth (if the gravitation of the Air &s;hould be admitted) would more than ten times counterpoi&s;e the next Mile about it, becau&s;e it hath the&s;e advantages, 1. of the greater incum|bent weight of the &s;uperior Air, 2. of the &s;tubborn re&s;i&s;tance of the terre&s;trial Globe, whereby it is more con&s;tipated and bound together the nearer it is to its reflexion and repercu&s;&s;ion. 3. The great concrement and acce&s;&s;ion that it hath of gro&s;&s;er vapors, and terre&s;trial effluxes, wherewith the lower parts mu&s;t needs be more laden than the up|per; &s;o that form the fir&s;t gravitating particle of Air or Atmo&s;phere to the lowe&s;t, it will increa&s;e by a Geometri|cal Progre&s;&s;ion in every part, as 1, 2, 4, 8, 16, or very near it, which will render the lowe&s;t Mile prodigiou&s;ly more weighty than any of the &s;uperior Miles.</P>
<P>But I di&s;mi&s;s this bu&s;ine&s;s of the gra|vitation of the free Air as a meer No|tion.</P>
<P>The In&s;tances to prove the Ela&s;ticity of the Air, are for the mo&s;t part &s;uch as
<PB N="207" REF="107">are endeavoured to be made out by the ten&s;ion or rarifaction of the Air by the Wind-pump, or <HI>Magdeburgh</HI> In&s;tru|ment. And the an&s;wer to any one of them gives an an&s;wer to all, for the ap|plication of them to the Ela&s;ticity or Spring of the included Air is bottomed upon one common mi&s;taken ground. I &s;hall therefore mention but one or two of them.</P>
<P>The Excellent Author in his Book of <HI>Phy&s;ico-Mechanical</HI> Experiments, <HI>Exp.</HI> 5. gives an account, how a dry Bladder well tied, and blown moderately full, and fa&s;tned into the in&s;ide of the Recei|ver in the Air-pump, upon a &s;trong ex|hau&s;tion of the Pump was broken; and in the 16^t^h Experiment, a Gla&s;s included in the Receiver, broken by the exhau|&s;ting of the Air. And in the Continu|ation of new Experiments, <HI>Exper.</HI> 7 and 9, the &s;ame In&s;tance of breaking of in|cluded Bladders and Gla&s;&s;es is repeted, and attributed always to the natural dilatation of the internal Air included in the Gla&s;s and Bladder, the circumja|cent Air being rarified by ten&s;ion.</P>
<PB N="208" REF="108">
<P>But the true Solution of both is quite another matter. The Bladder is dilated by the attraction wrought by the ten&s;ed or expanded Air, upon the out&s;ide of the Bladder, and thereby the included Air nece&s;&s;arily expanded by that force, &s;tretching out the &s;ides of the Bladder that includes it, and when it is capable of no greater &s;tretching it breaks, not by the natural expan&s;ion of the included Air, but by the &s;trong ten&s;ion wrought upon the Bladder by the attraction of rarified or ten&s;ed Air in the Receiver, that tears the Bladder.</P>
<P>And as to the Sealed Gla&s;&s;s-bubble, the fracture thereof with that violence is not by the natural Ela&s;ticity of the Air included in it, but by the &s;trong at|traction wrought upon every part of its external Superficies, by the ten&s;ion of the &s;trongly circumjacent ten&s;ed Air in the Receiver.</P>
<P>And therefore if the Bladder or Bub|ble were filled with Water, and clo&s;ed fa&s;t, (which is not capable of any natu|ral Ela&s;ticity) I make little que&s;tion but the &s;trong attraction of the expanded
<PB N="209" REF="108">Air in the Receiver would break the Gla&s;s and Bladder, e&s;pecially if it have any angles, (though I confe&s;s I cannot be very confident of what I never tried.)</P>
<P>And yet if it &s;hould &s;ucceed accor|ding as I &s;uppo&s;e, though the natural Ela&s;ticity of included Air would be thereby convinced of untruth; I expect there mu&s;t be another expedient inven|ted by the Elateri&s;ts to &s;alve it, <HI>viz.</HI> as prodigious a weight in the included Water, as there is &s;uppo&s;ed an Ela&s;ticity in the included Air.</P>
<P>In the late Book intituled, <HI>New Expe|riments about the Pre&s;&s;ure and Spring of Air upon Bodies under Water,</HI> Experi|ment the &s;econd, I find this Experiment, which is to the effect following.</P>
<P>Take a Bladder, and &s;queezing out the greate&s;t part of its Air, tye the neck very clo&s;e, and fa&s;tning a competent Weight to it, place it in a great large Gla&s;s, and placing that Gla&s;s upon the Air-pump, fill it with Water, and then covering the Gla&s;s with a large Recei|ver well luted to the Pump, the Air pumped out of the large Receiver, the
<PB N="210" REF="109">Bladder below the Water would gra|dually &s;well, 'till by often pumping out the Air, the Bladder would be full blown. And the Suppo&s;ition is this, that the Air being highly rarified and extended in the Receiver, whereby the &s;trength of its counterpre&s;&s;ure or Spring was weakned and abated; the little portion of Air in the Bladder, notwith|&s;tanding the interpo&s;ition of the Water, having the advantage thereby of expan|ding if &s;elf, did accordingly fill up the Bladder.</P>
<P>The truth of the fact is unque&s;tiona|ble, but the Solution of it by the natural Spring of the Air in the Bladder, is an a&s;&s;ignation of <HI>non cau&s;a pro cau&s;a;</HI> but the true Cau&s;e is, that by the &s;trong ten&s;ion of the Air in the Receiver, it lays hold and attracts upon all the parts of the Water, and all that is included in it, and the Bladder being within the reach of that forcible attraction, hath its &s;ides thereby di&s;tended, and the in|cluded portion of Air expanded and rarified by the ten&s;ion upon the Bladder; not by any natural Ela&s;ticity of the in|cluded
<PB N="211" REF="109">Air, but by the forcible attraction wrought upon the external Superficies of the Bladder, and pulling it a&s;under, whereby the included Air by the com|mon Law of Nature is nece&s;&s;arily ex|panded to prevent a vacuity.</P>
<P>And as if there had been no Water interpo&s;ed, the Bladder would thus have been extended, and the Air inclu|ded in it expanded, by the &s;trong attra|ction of the rarified Air in the Recei|ver; &s;o the &s;ame effect will as nece&s;&s;a|rily en&s;ue, notwith&s;tanding the inter|po&s;ition of the body of Water: for that <HI>vis attractiva</HI> of the expanded Air in the Receiver, though it immediately fa|&s;ten upon the Superficies of the Water in the ve&s;&s;el, yet thereby and there with it al&s;o pervades the whole body of the Water, which being a fluid body hath thereby a ten&s;ion made upon it, and all its parts, and all that is included in it.</P>
<P>And the truth of this appears beyond di&s;pute, for the Learned Author in his 19, 21, 22, 23, <HI>&amp;c</HI> Experiments, tels us, and that truly, that by this pumping and rarifying of the Air in the great Re|ceiver,
<PB N="212" REF="110">Water, Spirit of Wine, <HI>&amp;c.</HI> will be rai&s;ed to run out of a Gla&s;s included in it, &amp; that bubbles will thereby be for|med at the bottom of the included ve&s;|&s;el of Water: whereof the true cau&s;e (whatever be otherwi&s;e a&s;&s;igned) is the forcible attraction of the ten&s;ed and ex|panded Air in the Receiver upon the in|cluded Water, which &s;trongly per|vades the whole body of Water, pene|trates to the very fund or bottom of it, and puts it altogether into a various agi|tation.</P>
<P>And therefore as this attraction per|vades the whole body of water, &s;o it per|tingeth to the included Bladder in the very &s;ame manner as it doth upon the Water, though with a more &s;en&s;ible ex|tume&s;cence of the Bladder, becau&s;e more capable of it.</P>
<P>We need not re&s;ort to a more evident In&s;tance than that common and ludi|crous Experiment, yet taken notice of by <HI>Regius,</HI> of immer&s;ing the &s;mall end (<HI>Fig.</HI> 13.) of a lighted Tobacco-pipe <HI>B</HI> under Water in a Vial, and &s;ucking another Pipe <HI>C,</HI> not touching the water,
<PB N="213" REF="110">the Gla&s;s being clo&s;ely covered, the &s;trong attraction of the Mouth upon the one Pipe will, through the Water upon the orifice of the immer&s;ed Pipe, draw the Smoak into the other, not|with&s;tanding the interpo&s;ition of the Water, and will put all the parts of the Water, to the very bottom of it, and the granules of Sand lying at the bottom of the Water, into motion and elevati|on, as in the Figure.</P>
<P>And the very &s;ame An&s;wer is mo&s;t clearly to be given to the third and fourth Experiments in that place, and to others of like nature, without recur|ring to an imaginary natural Ela&s;tici|ty in a &s;mall portion of included Air, whereby to expand it &s;elf without any forcible attractions to &s;uch a prodigious amplitude.</P>
<P>And thus I have done with what I have to &s;ay again&s;t the Solution of the <HI>Torricellian</HI> Experiment, either by the Weight or Ela&s;ticity of the Air or At|mo&s;phere; which to me &s;eems a Sup|po&s;ition contradictory to our very Sen|&s;es, a Suppo&s;ition attended with infi|nite
<PB N="214" REF="111">ab&s;urdities and inexplicable diffi|culties.</P>
<P>And yet, as I have before &s;aid, it is wonderful to &s;ee with what tenacity, and with how great confidence it is a&s;|&s;erted, and how marvellou&s;ly it hath obtained among the <HI>gens literata,</HI> and what Sy&s;tems of new Phy&s;icks, what rare trains of Con&s;equences, what Pro|po&s;itions, <HI>pori&s;mata, Scholia,</HI> it hath mul|tiplied! wherein if the Foundation it &s;elf prove but a mi&s;take, men have &s;pent much labour in vain upon it.</P>
<P>Therefore laying a&s;ide this Solution as untrue, I proceed to that which the more &s;teady Modern Philo&s;ophers, con|&s;onant to the ancient Principles, have given in this ca&s;e, and &s;eems to be mo&s;t con&s;onant to truth.</P>
</DIV2>
<DIV2 N="15" TYPE="chapter">
<PB N="215" REF="111">
<HEAD>CHAP. XV.</HEAD>
<HEAD TYPE="sub"><HI>Concerning the true Cau&s;e of the &s;u&s;pen&s;ion of the Mercury at twenty nine Inches and half, or there about, in the <HI>Torricellian</HI> Engin.</HI></HEAD>
<P>I Come now to con&s;ider of that cau&s;e of the &s;u&s;pen&s;ion of the Mercury at twenty nine Inches and half, or therea|bouts, in the <HI>Torricellian</HI> Engin.</P>
<P>They that a&s;&s;ign the Diver&s;ity of the Weights of fluid Bodies, tell us; 1. That although Air be intrin&s;e|cally heavy, yet it is neer one thou&s;and times, or as <HI>Mer&s;ennus</HI> will have it, a|bout 1300 times lighter than the like quantity of Water; and this they en|deavour to evince by Experiments. But this Conclu&s;ion is very doubtful and difficult.</P>
<P N="2">2. That Water is fourteen times, or very neer thereabout, lighter than Mercury, quantity for quantity, and this as it is ea&s;ie to be tryed, &s;o upon try|al
<PB N="216" REF="112">I find it very neer the truth, though Water it &s;elf in &s;everal places differeth &s;omewhat in weight, and therefore it is not ca&s;ie to make this the common &s;tan|dard for all Waters, though the diffe|rence be not con&s;iderably great.</P>
<P>Though Water be ordinarily four|teen times lighter than Mercury, yet this is not the ju&s;t proportion of the &s;u&s;pen&s;ion of one and the other in a Tube.</P>
<P>For if a Tube of Water, above one and thirty foot long, &s;topt above and immer&s;ed at the other end in re&s;tagnant Water, it will &s;ub&s;ide as is ordinarily &s;aid to thirty and one foot, others &s;ay more, whereof &s;ee the Experiment <HI>apud Schottum in Technicis Curio&s;is, l. 3. cap. 2. Exper. 2, &amp; 3.</HI></P>
<P>But in the ca&s;e of Mercury, if the Tube of above twenty nine Inches and half long, &s;uppo&s;e four foot, be &s;topt at the top, and immer&s;ed at the open end in re&s;tagnant Mercury, it will &s;ub&s;ide to twenty nine Inches and half, or there|about.</P>
<P>But although in the&s;e two fluids, of
<PB N="217" REF="112">this different gravity, the &s;ub&s;iding of either vary, yet the rea&s;on both of the &s;ub|&s;iding and &s;u&s;pending of the one and the other will be the &s;ame.</P>
<P>Therefore what I &s;ay in relation to the &s;u&s;pen&s;ion and &s;ub&s;iding of Mercury, will be in its rea&s;on applicable to the other, and therefore I &s;hall here only treat of the &s;u&s;pending of Mercury, be|cau&s;e the In&s;truments to try the Expe|riment in Water are more ma&s;&s;y and un|tractable, but, as I &s;aid, the rea&s;on of one will be the rea&s;on of the other.</P>
<P>There be three In&s;tances of the &s;u&s;|pen&s;ion of the Mercury in the <HI>Torricel|lian</HI> Engin, which though they all are re&s;olvible into one common rea&s;on, yet that rea&s;on hath a various application &s;everally to them.</P>
<P>Fir&s;t, when the Tube exceedeth in length the ordinary &s;tation of the &s;u&s;|pended Mercury, <HI>viz.</HI> twenty nine In|ches and half, as &s;uppo&s;e it be four foot long, and the Tube receive only thirty Inches of Mercury, or though the Tube be filled more than twenty nine Inches and half of Mercury, yet it is not
<PB N="218" REF="113">&s;o perfectly filled, but that there remains a portion of Air in the head of the Tube, upon its inverting into the re&s;tagnant Mercury.</P>
<P>In this In&s;tance, if the portion of Air be &s;o great before its Expan&s;ion, that be|ing expanded by the de&s;cent of the Mer|cury, it can reach below twenty nine Inches and half, as &s;uppo&s;e to 20, 23, 24 Inches or le&s;s, then the Mercury will &s;ub&s;ide to that &s;cantlet that the portion of Air is extendible unto.</P>
<P>If the portion of Air be le&s;s than can be extended, below twenty nine Inches and half, or the di&s;tance be &s;o great that the exten&s;ion of that portion of Air can|not by its expan&s;ion &s;upply a greater room than what ju&s;t an&s;wers to that &s;tation: as &s;uppo&s;e the Tube were above 4 foot long, and filled with Mercury all but half an Inch, and then inverted into the ve&s;&s;el of re&s;tagnant Mercury, whereby before its &s;ub&s;iding there would be about half an Inch of free Air in the head of the Tube; and by the de|&s;cent of the Mercury to twenty nine In|ches and half if that little portion of
<PB N="219" REF="113">Air were yet &s;o much as were capable of &s;uch an exten&s;ion, it would be extended to that length, <HI>viz.</HI> eighteen Inches and half; but if that task were too hard for &s;o &s;mall a portion of Air to be extended unto, then the &s;ame would be &s;upplied by the &s;ub&s;idiary &s;teams and <HI>effluvia</HI> out of the Mercury, to make a retreat for the Mercury, to a de&s;cent of twenty nine Inches and half, as hath been &s;hewn, and &s;hall now farther be declared in what follows.</P>
<P>In this In&s;tance the&s;e things are to be noted. 1. That by the de&s;cent of the Mercury there is no vacuity left in the place derelicted by the Mercury, as hath been &s;hewn <HI>Chap. 2.</HI> That there is no new Air admitted into the Tube <HI>de foris,</HI> as hath been &s;hewn before, <HI>Chap. 3.</HI> But that little portion of Air is ex|tended from the very head of the cavity of the Tube to the &s;ub&s;ided Mercury, if it be of that &s;ub&s;tance that is capable of &s;uch an exten&s;ion to the Mercurial &s;ta|tion of twenty nine Inches and half: and if it be too little for &s;uch an exten|&s;ion, it is &s;upplied by a &s;uitable portion
<PB N="220" REF="114">of the Mercurial &s;teams, as hath been &s;hewn. 4. But that exten&s;ion or dilata|tion of that little portion of included Air, is not by any natural Elatery or ex|pan&s;ion of its own, as hath been &s;hewn in the two former Chapters, for it is a portion of the free Air; but it is a &s;trong ten&s;ion of that portion of included Air, to prevent that <HI>ca&s;ma</HI> and &s;eparation of Bodies without any thing intervening, or the <HI>fuga vacui,</HI> &s;o often mentioned by the Ancients. 5. And con&s;equently, though in relation to the laws of the Univer&s;e, it be a natural expan&s;ion or dilatation of the Air in this circum|&s;tance, <HI>in ob&s;equium naturae univer&s;alis,</HI> 01 yet in relation to the particular &s;tate and con&s;i&s;tence of that portion of the Air thus expanded or ten&s;ed by the &s;ub&s;iding of the Mercury, it is forced and violent. As the erect po&s;ture of my Body is natu|ral to me, while it makes one common compo&s;ition with my Soul and Spirits, and <HI>in Concreto,</HI> though it be violent in relation to the <HI>moles corporea</HI> of my Body, which would otherwi&s;e fall down to the Earth. 6. And the con&s;equence of
<PB N="221" REF="114">this ten&s;ion of the included portion of Air (con&s;idered conjunctly with the na|tural in&s;eparability of the parts of the Univer&s;e, which is all one with that which the Ancients called <HI>fuga vacui</HI>) is the &s;u&s;tentation of the Mercury, that column of de&s;cended Air, which <HI>Linus</HI> not ab&s;urdly calls <HI>funiculus,</HI> being in&s;e|parably united, and adhering to the top of the Tube at one end, and to the Mer|curial Cylinder at the other end, and this <HI>funiculus aereus</HI> not being capable to be extended farther than to twenty nine Inches and half, being the Mercurial &s;tation, by the force of the de&s;cent of the Mercury, &s;u&s;tains and holds it up at that &s;tation: and &s;o the <HI>pondus deprimens</HI> of the Mercurial Cylinder is equal to the <HI>potentia &s;uperne &s;u&s;tinens</HI> of the Aereal de&s;cended Cylinder upon it, in a kind of <HI>aequilibrium,</HI> the Mercurial Cylinder by its natural motion endeavouring its de&s;cent downward, and the aereal co|lumn by a motion of re&s;titution to its natural &s;ize and &s;taple, retracting it as much as it may upward; and the &s;ame rea&s;on will hold of the portion of inclu|ded
<PB N="222" REF="115">Air, be &s;o much as is capable of an exten&s;ion below twenty nine Inches and half of the Tube: but not &s;ufficient by &s;uch a force to be dilated to a full de|pletion of the Mercury out of the Tube, as po&s;&s;ibly to 20, 15, 10, or 5 Inches from the re&s;tagnant Mercury, in which ca&s;e the Mercury will &s;ub&s;ide to &s;uch a de|gree, and no lower.</P>
<P>The rea&s;on therefore, 1. Why the Mercury &s;ub&s;ides &s;o low as twenty nine Inches and half, its u&s;ual &s;tation, (or lower, if the portion of included Air be greater, as is before &s;aid) is, becau&s;e the weight of the de&s;cending Mercurial co|lumn is of that &s;trength, to give the in|cluded Air that ten&s;ion or dilatation. 2. Why it &s;ub&s;ides no lower, is becau&s;e when the Air hath attained its utmo&s;t ten&s;ion that the de&s;cent of that column of Mercury can give it (which ordinarily is at the height of twenty nine Inches and half) that aereal de&s;cended Cylin|der holds it there, and keeps it up to that height, the weight of the Mercury being now le&s;&s;en'd.</P>
<P>And that this is the cau&s;e of its &s;u&s;ten|tation,
<PB N="223" REF="115">appears evidently by the&s;e few In&s;tances. 1. If the Tube of Mercury in this &s;u&s;tentation be &s;uddenly lifted up from the re&s;tagnant Mercury, there will be a &s;trong re&s;ilition of the Mercu|ry towards the top of the Tube, that will endanger breaking it; as we &s;ee a Lute|&s;tring, if hanged upon a Nail, and o|vercharged with a Weight or &s;trength at the lower end, by which it breaks in the middle, the upper part of it will forcibly <HI>re&s;ilire</HI> in its contraction to its ordinary &s;ize. 2. If the Tube be incli|ned to a Level in the &s;ame parallel line to twenty nine Inches and half of the erected Tube, whereby it lo&s;eth its weight by the incumbence that it hath upon the &s;ides of the declined Tube, the Air will contract it &s;elf to its former con|&s;i&s;tency, which it had before that ten|&s;ion, being by this inclination of the Tube delivered from it.</P>
<P>And they that object again&s;t the ten|&s;ion of the Air in this ca&s;e; becau&s;e if it had a ten&s;ion in length, as the Lute|&s;tring hath, it would have likewi&s;e a contraction in its bredth, and &s;o would
<PB N="224" REF="116">not fill the Tube, mu&s;t remember that the Air is a ten&s;ible Body of &s;uch a na|ture, as is at the &s;ame time ten&s;ible in bredth as well as length, and in &s;uch its ten&s;ion as clo&s;ely adheres to the &s;ides of the Tube, as it doth at one end to the top of the Tube, and at the other end to the Mercurial column.</P>
<P>I &s;hall not here enlarge with In&s;tan|ces, to &s;hew, that the ten&s;ion of the Air, or any other ten&s;ible fluid. Body nece&s;|&s;arily effects attraction on the Bodies to which it is contiguous, but &s;hall re&s;erve that to the following Chapters: and I have been the longer in the explication of this In&s;tance, becau&s;e it fully opens the rea&s;on of the &s;econd In&s;tance, which now next follows. Therefore, 2. The &s;econd In&s;tance is, where a Tube clo&s;ed at one end, above twenty nine Inches long, &s;uppo&s;e it four foot long, is entirely filled with Mercury, and no Air admitted into it, and then inverted into a ve&s;&s;el of re&s;tagnant Mercury, without admi&s;&s;ion of any Air into it, either upon its inver&s;ion or im|mer&s;ion, (which though it be difficult,
<PB N="225" REF="116">may yet be done) in this ca&s;es the Mer|cury will &s;ub&s;ide to twenty nine Inches and half in the Tube.</P>
<P>This derelicted &s;pace of eighteen Inches and half, is, as I have before &s;aid, filled with a Mercurial &s;team or vapor, extracted out of the Mercury it &s;elf, and abraded from it by the de&s;cent and compre&s;&s;ion of the parts of that Mercu|rial column, as I have before &s;hewn <HI>Chap.</HI> and thereby likewi&s;e rarified or ten&s;ed, as the Air is in the former In|&s;tance.</P>
<P>And this being either real Air inclu|ded within the pores of the Mercury, and expre&s;&s;ed from it, or el&s;e a &s;ubtle Ingredient into the Mercurial compo|&s;ition, and extracted, and in its extra|ction dilated, as the Air is in the former In&s;tance. It performs the &s;ame office in relation to the &s;u&s;pen&s;ion of the Mer|cury, as the included extended Air did in the former In&s;tance, and therefore it need not to be repeated.</P>
<P>Only I &s;hall adde this farther, 1. That it appears the extraction of the &s;ubtle <HI>effluvia,</HI> and their dilatation, is perform|ed
<PB N="226" REF="117">with a great &s;tre&s;s or &s;training of them out of the Mercurial Body, and with little le&s;s labour extended; which appears by the &s;low de&s;cent of the Mer|cury, ari&s;ing from the <HI>lucta</HI> or conte&s;t that grows between the weight of the Mercury de&s;cending on the one hand, and the &s;training and abrading of tho&s;e &s;ubtle particles, and their ten&s;ion or rarifaction of the other hand. And the like &s;low de&s;cent there appears in the fir&s;t In&s;tance, e&s;pecially as the Mer|cury more and more &s;ub&s;ides; for then the Mercury having neer acquired its ordinary &s;tation, grows lighter, and the &s;trength of its pre&s;&s;ure begins utterly to langui&s;h and decay too, being neer equally matched with the <HI>potentia &s;u&s;ti|nens</HI> of the extracted &s;ubtilized particles in this In&s;tance, and by the ten&s;ion of the Air in the former in&s;tance; the rea|&s;on whereof &s;hall be farther enlarged, when I come to the third In&s;tance. 2. Whereas in the former In&s;tance, by the inclining of the Tube, the Air re|gains its former contracted extent, here by the inclining of the Tube the&s;e &s;ub|tle
<PB N="227" REF="117">particles extracted out of the Mercu|ry, and dilated, are not only contracted, but refumed into the Mercury from which they were extracted, as is &s;hewn in the Chapter. 3. That upon the over &s;udden Elevation of the Tube out of the re&s;tagnant Mercury, there will be the like re&s;ilition of the Mercury into the top of the Tube, as in the former in|&s;tance.</P>
<P>By this <HI>funiculus &s;ubtilis materiae</HI> the Mercurial column is &s;u&s;tained at twen|ty nine Inches and half, as in the former In&s;tance of the <HI>funiculus aereus.</HI></P>
<P>But now how it comes to pa&s;s, that &s;ince there is yet remaining twenty nine Inches and half in the Tube, which doubtle&s;s hath a re&s;idue of &s;ubtle matter extractable out of it, to &s;upply a grea|ter room, that what is yet left above twenty nine Inches and half, how it comes to pa&s;s that by the weight of that twenty nine Inches and half of Mercu|ry, there is not more of the Mercurial effluxes extracted and dilated, which may give a total de&s;cent and evacuation of the Mercurial column into the re|&s;tagnant
<PB N="228" REF="118">Mercury remains to be con|&s;idered, which &s;hall be done in the third In&s;tance which follows.</P>
<P N="3">3. The third in&s;tance is, when the Tube is but ju&s;t twenty nine Inches and half, or &s;horter, &s;uppo&s;e 25, 20, 10, or 5 Inches long, and filled entirely with Mercury, and then inverted into the ve&s;&s;el of re&s;tagnant Mercury; in that ca&s;e the entire Mercury will remain &s;u&s;|pended, and remain contiguous to the top of the Tube, and no part will de|&s;cend, neither will there be any &s;uch <HI>funiculus</HI> of Air or &s;ubtle Matter to con|nect it to the top of the Tube.</P>
<P>The rea&s;on of this is what in effect was given in the former in&s;tances, though the application be di&s;&s;erent.</P>
<P>Fir&s;t, if in this in&s;tance the Mercury &s;hould any whit &s;ub&s;ide, either it mu&s;t leave the <HI>inter&s;titium</HI> between it &s;elf and the top of the Tube vacant of any Body, or it mu&s;t yeild &s;ome &s;ubtle matter to &s;upply the place it leaves abraded from it &s;elf, as in the &s;econd In&s;tance. And if it can do neither of the&s;e, <HI>manet &s;ors tertia,</HI> only to continue its &s;tation united to the top of the Tube.</P>
<PB N="229" REF="118">
<P>The former of the&s;e cannot be, for I have &s;uppo&s;ed, and &s;hall further inforce the contradiction of the Law of the U|niver&s;e to that Suppo&s;ition.</P>
<P>Therefore it remains, that either there mu&s;t be a &s;ubtle matter extracted out of the included Mercury, or of nece&s;&s;ity the Mercury mu&s;t hold its entire po&s;|&s;e&s;&s;ion of the whole Tube.</P>
<P>Although the remote cau&s;e of this extraction of &s;ubtle parts out of the Mercury, in the &s;econd In&s;tance, be that law of the Univer&s;e, to hold toge|ther the continuity of its parts, and con|&s;equently to avoid a <HI>vacuum</HI> or <HI>ca&s;me</HI> in the Univer&s;e de&s;titute of matter; yet the immediate cau&s;e of this extraction and rarifaction is the de&s;cent of the Mer|cury from the &s;tation that it hath, and the weight of its Body is the cau&s;e of that de&s;cent.</P>
<P>And becau&s;e it requires a &s;trong com|pre&s;&s;ion of the Mercury, either to drive or draw out this &s;ubtle matter, and as it were to rake it out of the bowels of the Mercury, and to extend it, and con&s;e|quently a &s;trong weight to effect that
<PB N="230" REF="119">compre&s;&s;ion and exten&s;ion, if that weight which it hath at 29 Inches and half, or under, be not effective of &s;uch an abra&s;ion or exten&s;ion of the &s;ub|tle matter &s;o abraded; &s;uch abra&s;ion or exten&s;ion not being effectible by that weight, the column of Mercury mu&s;t hold its po&s;ition, and becomes its own <HI>funiculus,</HI> and remain &s;u&s;pended to the top of the Tube.</P>
<P>Now it &s;eems, that although a Mer|curial Cylinder of a height above thirty Inches, as &s;uppo&s;e three or four foot, hath &s;uch a forcible pre&s;&s;ure, weight, and gravitation upon the re&s;tagnant Mercury, not only to drive down the Mercurial Cylinder to twenty nine Iches and half, but al&s;o to extract and &s;train out of it, and extend a &s;ufficient portion of &s;ubtle matter out of the Mer|curial Body to &s;upply the room it leaves; yet that the weight only of twenty nine Inches and half, or below it, will not be able to drive, or draw out, or extend a portion &s;ufficient for that Exigent.</P>
<P>And that is the rea&s;on, why at twen|ty nine Inches and half, or under that
<PB N="231" REF="119">gage, whether the Tube be ju&s;t twenty nine Inches and half, or longer; yet the Mercurial Cylinder re&s;ts there, wanting a &s;ufficient <HI>potentia</HI> below that &s;tation by its weight, to extract or to rarifie any of its &s;ubtle parts, to &s;upply the place which then it &s;hould de&s;ert or leave.</P>
<P>And herein the bigne&s;s or &s;mallne&s;s of the Gla&s;s Tube, or the Mercurial Cy|linder included, makes no odds; though po&s;&s;ibly according to the various dia|meters of the Tubes, one Cylinder of Mercury of 29 Inches and half high, may weight five times another Cylinder of the &s;ame height, and yet both would remain &s;u&s;pended in the Tubes.</P>
<P>But the di&s;parity of the <HI>potentia de|primens,</HI> is from the di&s;parity of the height of the Tube. And therefore the cau&s;e why the Cylinder of Mercury, filling a Tube of 3 or 4 foot long, will &s;ub&s;ide upon inver&s;ion unto twenty nine Inches and half, and there &s;tay, is, be|cau&s;e before its de&s;cent to that &s;tation, its <HI>potentia</HI> was &s;ufficient to abrade and extend the &s;ubtle matter, but at twenty nine Inches and half that <HI>potentia</HI> was &s;pent.</P>
<PB N="232" REF="120">
<P>And therefore the rea&s;on why the Tube of twenty nine Inches and half, or under, doth not &s;ub&s;ide at all, but re|mains cohering to the top of the Tube, is, becau&s;e it hath not that <HI>potentia</HI> at that gage to abrade from it &s;elf matter to &s;upply that place, if it &s;hould leave it.</P>
<P>And for this purpo&s;e it will not be ami&s;s to take notice of what <HI>Galilaeus,</HI> and after him the Excellent <HI>Mer&s;ennus</HI> have given us in relation to the di&s;pa|rity of the <HI>motiva pote&s;tas</HI> of the &s;ame fiu|id in different po&s;itions of height or ele|vation.</P>
<P>The acceleration of motion of heavy Bodies is <HI>ut quadr at a temporum,</HI> in which they move downwards; as if in the fir&s;t Minute, a Body moves one foot, in the &s;econd minute it will move four foot, <HI>viz.</HI> two times two; in the third minute nine foot, <HI>viz.</HI> three times three; or, which comes to all one ac|count, heavy bodies in their de&s;cent, in every given portion of time, as a minute will percur portions of &s;pace <HI>per numeros impares ab unitate;</HI> as if in the fir&s;t mi|nute
<PB N="233" REF="120">it de&s;cend one foot, in the &s;econd it will de&s;cend three foot, in the third five foot, in the fourth minute &s;even foot, and &s;o onward.</P>
<P><HI>Mer&s;ennus</HI> partly upon this, Theory, and partly upon his own experience, makes two Conclu&s;ions, (which I have experimentally found true) that are ap|po&s;ite to explicate what I mean in this matter.</P>
<P>Fir&s;t, if there be two ve&s;&s;els of equal height, but of differing diameters, and with an equal <HI>lumen</HI> or hole in the bot|tom of each of them, and both filled with Water; the &s;maller ve&s;&s;el will in the &s;ame portion of time empty from it &s;elf as great a quantity of Water as the greater, for the Gravitation of the Wa|ter upon the <HI>Lumen</HI> is <HI>&s;ecundum altitu|dinem,</HI> not <HI>&s;ecundum latitudinem va&s;is:</HI> and upon the &s;ame account it is, that if the <HI>lumen</HI> be at the &s;ide, and the ve&s;&s;els be placed in the &s;ame horizontal paral|lel, the Parabolical line made by &s;alient Water out of each ve&s;&s;el, will be of the &s;ame length and amplitude.</P>
<P N="2">2. That if there be two Tubes or
<PB N="234" REF="121">ve&s;&s;els of Water, <HI>A</HI> and <HI>B,</HI> of the height of nine foot, containing nine Gallons of Water, and <HI>B</HI> were a ve&s;&s;el of &s;ixteen foot containing &s;ixteen Gal|lons of Water, and each ve&s;&s;el had a &s;mall <HI>lumen</HI> in the &s;ide next to the Ba&s;e, of equal bigne&s;s, and of that bigne&s;s, that were there but one Gallon in the Tube, it would empty that Gallon in one minute. In the&s;e In&s;tances, <HI>A</HI> fil|led with Water would empty five Gal|lons in the fir&s;t minute, three Gallons in the &s;econd minute, and one Gallon in the la&s;t minute. Again <HI>B,</HI> if filled with Water, would empty &s;even Gallons in the fir&s;t minute, five in the &s;econd mi|nute, and three in the third minute, <HI>viz. in ratione &s;ubduplicata altitudinis.</HI> And this I have experimentally found to be true.</P>
<P>The con&s;equence whereof is, that e|very fluid Body the higher it is eleva|ted, hath the greater and more effectual pre&s;&s;ure by its po&s;ition upon its lower parts or other fluid, than what barely ari&s;eth from its weight: &s;o that in a co|lumn of Mercury in a Tube of four foot
<PB N="235" REF="121">high, though the lowe&s;t foot and the highe&s;t foot of Mercury be of an equal weight, yet the pre&s;&s;ure of the upper|mo&s;t or fourth foot, which I call its <HI>po|tentia deprimens,</HI> is to the third as &s;even to five, and the third to the &s;econd is as five to three, and the &s;econd to the fir&s;t as three to one, namely when it hath a liberty of de&s;cending motion, as the Mercury hath in this Experiment; for the intermediate weight contributes to the pre&s;&s;ure of the uppermo&s;t foot.</P>
<P>And hence it is that the power to &s;e|rate and &s;egregate, and &s;train, and ex|tend the &s;ubtle matter out of the Mercu|ry, is vigorous and effective in a Mercu|rial column of 4 foot high, and gradually is le&s;s and le&s;s 'till it come to twenty nine Inches and half; and then though it hath a con&s;iderable Gravitation, yet it is not equal to effect &s;uch a &s;eparation, and therefore mu&s;t needs &s;tand &s;u&s;pended at that height, or leave a <HI>vacuum</HI> behind it, which the Catholick laws of the Uni|ver&s;e do not permit.</P>
<P>And thus far touching the Explicati|on of the Solution, which &s;eems to me
<PB N="236" REF="122">to be the true Solution of the <HI>Torricelli|an</HI> Experiment.</P>
<P>And in the next place I &s;hall &s;ubjoin &s;ome In&s;tances that &s;eem to me to con|firm it, and an&s;wer &s;ome Objections that are made again&s;t it.</P>
</DIV2>
<DIV2 N="16" TYPE="chapter">
<HEAD>CHAP. XVI.</HEAD>
<HEAD TYPE="sub"><HI>Concerning the two Suppo&s;itions that are ne|ce&s;&s;ary to maintain this Solution,</HI> viz <HI>Natures abhorrence of</HI> vacuum, <HI>and the Attraction of ten&s;ible fluids, or other bo|dies when under a ten&s;ion.</HI></HEAD>
<P>THere are two Suppo&s;itions that are nece&s;&s;ary to be proved, to render the Solution above given evident or probable. I. The exclu&s;ion of a <HI>vacuum</HI> or &s;pace in the Univer&s;e wholly empty of any Body. 2. That any Body, capa|ble of ten&s;ion, or rarifaction by ten&s;ion, (&s;uch as are the Air and thin <HI>effluvia</HI> of Mercury) to be attractive upon the con|tiguous Bodies, when actually under that ten&s;ion.</P>
<PB N="237" REF="122">
<P N="1">1. As to the former of the&s;e, I need not much labour for it, upon two rea|&s;ons. 1. Becau&s;e there have been large Tractates upon this Po&s;ition, and to re|peat them would be but <HI>actum agere.</HI> 2. Becau&s;e the exclu&s;ion of the Gravita|tion and Ela&s;ticity of the Air, invented or &s;ub&s;tituted by the modern Elateri&s;ts, doth nece&s;&s;arily conclude, that there can be no <HI>vacuum</HI> in Nature; for all tho&s;e Experiments and In&s;tances, which they produce to prove that Gravitation or E|la&s;ticity, and by which they go about to &s;olve them, mu&s;t (if tho&s;e Solutions prove untrue, or ineffectual) of nece&s;&s;ity maintain that ancient Peripatetical po|&s;ition, becau&s;e they are uncapable of any other Solution. And in my judgment that Gravitation and Ela&s;ticity of the common Air is &s;ifficiently convinced by what hath been before &s;aid touch|ing it.</P>
<P>And when I meet with tho&s;e Obje|ctions that I find u&s;ed by Learned men, namely how the Mercury or Water comes to know there will be a <HI>vacuum,</HI> if they do not leave their natural Gra|vity,
<PB N="238" REF="123">and &s;o a&s;cend or remain &s;u&s;pended to &s;upply it, and how tho&s;e &s;tupid inani|mate Elements or Minerals come to un|der&s;tand, that Nature &s;o much abhor|reth a <HI>vacuum;</HI> are much of the &s;ame kind, as if a man &s;hould ask the Sun, if it move according to <HI>Ptolemy;</HI> or the Earth, if according to <HI>Copernicus</HI> it move; how they came to know that when they come to the Northern Tropick, they mu&s;t move again to the Southern Tropick? or when it hath touched the Southern Tropick, it knows that it mu&s;t come back to the Northern, and &s;teer its cour&s;e accordingly? Or as if a man &s;hould ask, how doth the Stone under|&s;tand that he mu&s;t de&s;cend, when yet all the men in the world can never give any &s;atisfactory rea&s;on for its mo|tion to the Earth, more than to the Moon, but only Nature that is the <HI>prin|cipium motus &amp; quietis,</HI> or rather the God of Nature, who&s;e &s;tanding and &s;tatumi|nated Law Nature is, hath &s;o order'd it, and ordered &s;o in the be&s;t way for the u&s;e, beauty, and accommodation of the Univer&s;e. The plain truth of it is, the
<PB N="239" REF="123">very con&s;ideration of the many attempts that have been made to explicate the rea&s;on of the de&s;cent of heavy Bodies, is enough to let us &s;ee, that we tire our &s;elves in vain to determine the clear rea&s;on of it, without re&s;olving it into the &s;tatuminated Law of Nature: though the Stone and the Earth are ina|nimate, or at leaft unrea&s;onable Bodies, &s;uch kind of Objections therefore as the&s;e are fond and weak.</P>
<P N="2">2. As to the &s;econd, namely the at|traction of Bodies extended, whether by rarifaction or ten&s;ion, e&s;pecially of the Air, or this &s;ubtle matter that ari&s;eth from the Mercury. This affection and effect is as natural as any thing in Na|ture, as is truly ob&s;erved by the learned <HI>Fabri, in primo tractatu phy&s;ico, prop.</HI> 205, 206, 208. For a &s;trict contiguity in all parts of &s;everal Bodies is a kind of con|tinuity of the Univer&s;e and all its parts; neither can I imagine how tho&s;e that are fond of the <HI>Epicurean hypothe&s;is,</HI> can better maintain the cohe&s;ion of the parts of &s;olid bodies, their <HI>atomi hamati</HI> being but fancies of what men never &s;aw in them.</P>
<PB N="240" REF="124">
<P>The Air is the common cement and connecter of the different parts of this in|ferior world at le&s;t, and &s;trictly inter|po&s;eth between their fi&s;&s;ures and <HI>inter|&s;titia,</HI> to maintain a kind of common continuity between the different parts of the Univer&s;e, and makes it as it were one continued Body.</P>
<P>But to come to particular In&s;tances, which &s;hall not be laborious but familiar and common, to evince this cohe&s;ion of the parts of ten&s;ed or rarified Air, and the contraction that it makes upon con|tiguous bodies, in its endeavour of re|&s;titution to its natural &s;tate and con&s;i|&s;tence.</P>
<P N="1">1. The in&s;tance of Cupping-gla&s;&s;es, where the Air is highly rarified or eva|cuated by the included burning Tow, and applied to the fle&s;h, draws up the fle&s;h &s;trongly unto it, when by the ex|tinction of the Tow the rarified Air con|tracts it &s;elf to a narrow room, which can be no otherwi&s;e than by the cohe|&s;ion of the particles of Air to the skin, and driving it in to the Gla&s;s, while it contract, it &s;elf to a narrower
<PB N="241" REF="124">compa&s;s. And certainly they that tell us, that this is done by the pre&s;&s;ure of the ambient Air upon the contiguous fle&s;h, which thru&s;ts it up into the Gla&s;s, either do not believe them&s;elves while they &s;ay it, or are &s;o tran&s;ported with a love unto or ingagement for their belo|ved <HI>hypothe&s;is,</HI> of the prodigious gravi|tation of the free Air, that they are con|tent to &s;ay any thing in its behalf.</P>
<P><HI>Qui amant ip&s;i &s;ibi &s;omnia fingunt.</HI></P>
<P><HI>Shottus</HI> (who while he wrote his <HI>mi|rabilia hydraulica,</HI> was well &s;atisfied with the Solution of the <HI>Torricellian</HI> Experi|ment by the common Solution of <HI>fuga vacui</HI>) was indeed afterward, when he wrote his <HI>mirabilia Magdeburgica,</HI> con|verted to the new Solution, being not willing it &s;eems to be thought to &s;ee le&s;s in Nature than the new Tribe of <HI>Virtuo&s;i</HI> that were concerned in that Engine. But for all that, this In&s;tance of Cup|ping-gla&s;&s;es was too hard for that new Solution, and were fairly fain to have recour&s;e to the <HI>decantata fuga vacui,</HI> or el&s;e it mu&s;t &s;tand un&s;olved, and &s;o mu&s;t any el&s;e that means an impartial and
<PB N="242" REF="125">unpreingaged &s;earch into Nature.</P>
<P N="2">2. If an empty Bladder be tied clo&s;e about the neck, and fa&s;tned to the top of the Tube, Hermetically &s;ealed in the <HI>Torricellian</HI> Experiment, upon the &s;ub|&s;iding of the Mercury the Bladder will be expanded, not by the natural Elate|ry of the little particle of included Air, but by the &s;trong attraction of the ten&s;ed Air in the Tube, by the de&s;cent of the Mercury, whereof before.</P>
<P N="3">3. The In&s;tance given in the tenth Chapter, of the Tube heated, and ap|pended to a Ballance, &s;o as it touch the Water, the Water ri&s;ing in the Tube, the Tube will be drawn down, which is only done by the adhe&s;ion of the two extremes of the inclo&s;ed rarified Air, the one Extreme laying hold upon the top of the cavity of the Tube, the other end laying hold of the Water, and drawing it up, and therewith nece&s;&s;arily drawing the Tube down, whil&s;t the included Air is contracting if &s;elf to its natural and narrower dimen&s;ions.</P>
<P>And becau&s;e the Experiment made by a wide-mouth'd Gla&s;s would yeild
<PB N="243" REF="125">&s;ome di&s;coveries of this attraction by the rarified Air, which are not &s;o vi&s;ible in &s;o narrow a Tube, I took a Beer-gla&s;s, as in the <HI>Figure</HI> 14, and &s;u&s;pended it by a Thrid to one Scale of the Ballance, and weighing it with a weight in the op|po&s;ite Scale, and found it weight two Ounces and half; then, as we u&s;ed when we were School-boyes, &s;ticking up a Candle in a Ba&s;on, I let down the Gla&s;s over the Candle contiguous to the Superficies of the Water, the Can|dle going out there was a portion of Water drawn up into the Gla&s;s, the Air upon the Candles going out, and the Gla&s;s drawn down into the Water, the included Air being under a cau&s;e of ra|rifaction, namely by the heat of the Candle, and by the extinction of the Flame now gradually contracting it &s;elf, and thereby drawing up the Water to &s;upply that place.</P>
<P>The water drawn up into the gla&s;s was about half an Inch; we marked exactly the weight that was required now to lift up this Gla&s;s and included water was an addition of 4 Ounces and &frac14; &frac18; of an
<PB N="244" REF="126">Ounce; &s;o that the whole weight that rai&s;ed the Gla&s;s and Water inclo&s;ed, and &s;evered it from the Water beneath, was &s;ix Ounces &frac12; &frac14; &frac18; of an Ounce, and then, though not without reluctance, the Gla&s;s was rai&s;ed out of the Water.</P>
<P>Then taking the exact quantity of other Water, equall to that formerly included in the Gla&s;s, (which was not difficult to do by the help of the remai|ning Mark) we weighed it, and found it to weight exactly three Ounces and half, and a very few Grains.</P>
<P>So that the weight of the Gla&s;s and inclo&s;ed Water amounting to &s;ix Oun|ces, there was requi&s;ite an addition of about half an Ounce to &s;ever the Gla&s;s from the Superficies of the re&s;tagnant Water, which did apparently to the eye and touch adhere together, not|with&s;tanding the counterpoi&s;e of &s;ix Ounces, equal to the weight of the Gla&s;s and included Water.</P>
<P>And this half Ounce of additional weight was due purely to the adhe&s;ion of the gla&s;s, Air, &amp; inclo&s;ed water to the Superficies of the re&s;tagnant Water.</P>
<PB N="245" REF="126">
<P N="1">1. It &s;eems evident, that not only the Gla&s;s, but the Water included in it, gravitates upon the Scale, for the coun|terpoi&s;e of &s;ix Ounces in the oppo&s;ite Scale, equals the weight both of the Gla&s;s and Water inclo&s;ed in it, which could not be, unle&s;s both contributed to the <HI>aequipondium.</HI></P>
<P N="2">2. That it is impo&s;&s;ible that the in|cluded Water could gravitate upon the Scale, unle&s;s the rarified Air were con|tiguous and cohering to the top of the Gla&s;s, and al&s;o to all the parts of it in|cluded within the cavity of the Gla&s;s above the Superficies and whole body of the included Water, and al&s;o firmly adhered to the Superficies of the inclu|ded Water, for they all make up but one common weight, and there mu&s;t be a <HI>vinculum</HI> that mu&s;t connect the Gla&s;s and the inclo&s;ed Water, and otherwi&s;e they could not gravitate together; &s;o that the <HI>vinculum</HI> that binds the Water to the Gla&s;s is this <HI>funiculus</HI> (as <HI>Linus</HI> well calls it) of the rarified Air, as the Thrid is the <HI>vinculum</HI> that binds the Gla&s;s to the Scale: for otherwi&s;e the
<PB N="246" REF="127">Gla&s;s would be only rai&s;ed, and leave the Water to &s;ub&s;ide into the ve&s;&s;el of re&s;tagnant Water, and would never hold an <HI>aequipondium</HI> to more than two Oun|ces and a half, which was the ju&s;t weight &s;ingly of the Gla&s;s.</P>
<P>But as for the fancy above mentioned, <HI>Chap.</HI> 10. that it is not the Gla&s;s and Water that make up the weight of &s;ix Ounces, but the Gla&s;s and the column of Air incumbent upon it, the vanity of that imagination is &s;ufficiently convin|ced in that Chapter.</P>
<P N="3">3. That con&s;equently, the included rarified Air thus fa&s;tning upon the ca|vity of the Gla&s;s and the included Wa|ter by a &s;trict cohe&s;ion, according to the nature of ten&s;ed fluids, contracting it &s;elf as much as it can by its motion of re&s;titution, draws up the Water in the ve&s;&s;el into the Gla&s;s, and rai&s;eth it as high, 'till there be an <HI>aequilibrium</HI> be|tween the <HI>pondus naturale deprimens</HI> of the Water, and the <HI>potentia &s;u&s;tinens</HI> of the Air, thus now contracting it &s;elf, and indeavouring its re&s;titution to its ju&s;t natural dimen&s;ion.</P>
<PB N="247" REF="127">
<P N="4">4. As a <HI>&s;pecimen</HI> of this cohe&s;ion of the Air and Water included in the Gla&s;s, there is al&s;o a cohe&s;ion of the Limb of the Gla&s;s and the included Water unto the Superficies of the re&s;tagnant Water, which requires half an Ounce of weight to break that continuity between the upper and lower Water. And no other imaginable cau&s;e can be a&s;&s;igned for it, but that <HI>Natura aegr&egrave; patitur disjunctio|nem partium continui.</HI></P>
<P>And as with the hand you lift up the Gla&s;s towards the Superficies of the re|&s;tagnant Water, the Water included will ri&s;e with it much above the Super|ficies of the external Water, which can|not be by the imaginary pre&s;&s;ure of the external Air, but by the adhe&s;ion of the column of Water to the included ten|&s;ed Air, and of that to the concave Su|perficies of the Gla&s;s <HI>per modum unius con|tinui,</HI> which any man's tryal will make more plain and evident to him, than words in writing can ea&s;ily expre&s;s.</P>
<P>But &s;ome exception is taken to the word <HI>funiculus,</HI> and we are asked what Grappers there are belonging to this <HI>fu|niculus,</HI>
<PB N="248" REF="128">that can &s;o &s;teadily lay hold of the Water and the Gla&s;s, and hold them thus tight togher?</P>
<P>And I mu&s;t confe&s;s, that I wonder, that any that approves the Atomical or Epicurean Philo&s;ophy, can make that Que&s;tion, &s;ince all their pretence of the cohe&s;ion of the imaginary Atomical Particles in any the mo&s;t &s;olid <HI>continu|um,</HI> are certain <HI>atomi hamati,</HI> that in|terlock one in another, which yet they never &s;aw.</P>
<P>But let it be: I an&s;wer, the power of the laws of Nature are &s;o efficacious, that they can and do colligate &s;trictly parts even of mo&s;t di&s;tantial textures and con&s;i&s;tences, without the help of Vellicle, Hooks, or Grappers. What are the Hooks or Grappers, whereby the Humane Soul and Body, yea the Souls and Bodies of Animals are knit together, whereby the Bloud and the Spirits are colligated, whereby the Load|&s;tone attracts the Iron, notwith&s;tanding an interpo&s;ed Plate of Bra&s;s or body of impervious Gla&s;s, and a thou&s;and more In&s;tances of Attraction between Bodies,
<PB N="249" REF="128">without the intervention of &s;en&s;ible Grappers and Hooks, or &s;uch gro&s;s Mechani&s;mes.</P>
<P>This, and &s;ome other as light as this, and &s;ome toying with the word <HI>funicu|lus,</HI> are the greate&s;t Objections that I find again&s;t what <HI>Linus</HI> hath in this matter delivered, which &s;eem to me of no moment. Words were made to ren|der Conceptions of things, and if they do that, they do their office.</P>
<P>And thus far concerning the Soluti|on of the <HI>Torricellian</HI> Engin. I &s;hall adde a few words, as I promi&s;ed, touching the cohe&s;ion of two poli&s;hed Marbles, and the in&s;ufficiency of the Solution thereof given by the Elateri&s;ts, and the truth of the ancient Solution thereof.</P>
</DIV2>
<DIV2 N="17" TYPE="chapter">
<PB N="250" REF="129">
<HEAD>CHAP. XVII. <HI>Concerning the Cau&s;e of the Cohe&s;ion of two poli&s;hed Marbles.</HI></HEAD>
<P>THere are two Experiments, for the Solution whereof the Gravitation and Elatery of the Air is by the late Phi|lo&s;ophers applied, which in this la&s;t place I &s;hall examine according to my premi&s;ed method.</P>
<P>The fir&s;t is that of the cohe&s;ion of two poli&s;hed Marbles. For in&s;tance, take two poli&s;hed Marbles, of one dimen&s;ion and figure, and exactly in the centre of each Marble let there be a Ring, where|by to &s;u&s;pend the upper, and whereby a weight may be appended to the lower. The&s;e two Marbles, e&s;pecially if their &s;mooth &s;ides be a little oyled, and applied each to other, will adhere &s;o &s;trongly together, that the upper being &s;u&s;pended by its Ring to a po&s;t or frame, (<HI>Fig.</HI> 15.) the lower will &s;u&s;tain a weight of 20, 30, or 40 pounds, though the
<PB N="251" REF="129">Marbles be not above three Inches dia|meter.</P>
<P>And as it will do this in the open Air, it will al&s;o perform the &s;ame, though the Marbles be inclo&s;ed within a clo&s;e large Gla&s;s-Receiver, whereby it is &s;eve|red from the common Air, or any im|pending column of the Atmo&s;phere.</P>
<P>The rea&s;on that the vulgar Philo&s;o|phers were wont to give in the&s;e ca&s;es are the&s;e: Fir&s;t, as to the &s;trict cohe&s;ion of the two Marbles, they give this rea&s;on; that the cohe&s;ion is <HI>ob fugam vacui.</HI> For if they &s;hould be &s;evered by the appended weight, the &s;eparation of them would be in the &s;ame indivi&s;ible moment, be|cau&s;e they do <HI>contingere in puncto.</HI></P>
<P>And in as much as all Bodies move &s;ucce&s;&s;ively, and not in an in&s;tant, it would be impo&s;&s;ible for the circumam|bient Air in the moment of the &s;epara|tion of the&s;e two Marbles, to pervade the whole <HI>inter&s;titium</HI> that would hap|pen upon the fir&s;t &s;eparation, and con|&s;equently there would be a mean time wherein the <HI>inter&s;titium</HI> would remain
<PB N="252" REF="130">empty, therefore the cohe&s;ion is &s;o ob|&s;tinate to prevent that mon&s;ter in Na|ture, namely <HI>vacuum.</HI></P>
<P>And to evidence that this is the rea|&s;on, they &s;ay that if the aperture be at|tempted at the &s;ides, either by pulling them at one &s;ide, or by appending the weight more to one &s;ide than the other, they are ea&s;ily &s;eparated, becau&s;e that aperture makes an Angle, (<HI>Fig.</HI> 16.) and gradually admits the Air into it; for then the aperture is not all at once, but is <HI>apertio continuata</HI> from the fir&s;t ope|ning. For although if the Ba&s;e of the acute Angle, <HI>viz. A,</HI> were but a hairs breadth, the Angle were divi&s;ible Ma|thematically unto the uttermo&s;t extre|mity of it; yet it is not &s;o Phy&s;ically, it but gains a &s;ucce&s;&s;ive latitude, accor|ding as it gradually opens, and &s;o is ac|commodated Phy&s;ically to a &s;ucce&s;&s;ive intromi&s;&s;ion of the Air: but if the aper|ture were altogether, the &s;eparation in all parts of the Superficies mu&s;t be Phy|&s;ically as well as Mathematically in the &s;ame in&s;tant, which were too quick to give an admi&s;&s;ion to the &s;ucce&s;&s;ive mo|tion
<PB N="253" REF="130">of the aery body in the &s;ame in&s;tant.</P>
<P>But now we will con&s;ider what So|lutions the late Philo&s;ophy gives in this in&s;tance.</P>
<P>Namely I. That in the free and open Air there is an impending column of Atmo&s;phere, reaching from the &s;ummi|ty thereof to the upper Marble, and com|men&s;urate in its diameter and circumfe|rence to the <HI>area</HI> of the upper Marble that pre&s;&s;eth it, with an exce&s;&s;ive weight downwards, and &s;o upon the upper Hemi&s;phere if &s;u&s;pended parallel to the Horizon.</P>
<P N="2">2. That again there is a returning or recoiling Cylinder of Air, reaching from the Superficies of the Earth up|wards, of as great a <HI>potentia &s;u&s;tinens</HI> as the &s;uperior column of Atmo&s;phere hath a <HI>pondus deprimens:</HI> and this infe|rior or re&s;ulting column is commen&s;u|rate al&s;o in its diameter and circumfe|rence to the lower Marble, or brazen Hemi&s;phere, and thru&s;ts that as vigo|rou&s;ly up to the upper Marble, as the upper column pre&s;&s;eth downward. And &s;o the <HI>potentia &s;u&s;tinens</HI> being equal to
<PB N="254" REF="131">the <HI>pondus deprimens,</HI> the lower Marble is able to &s;u&s;tain a weight equal to the weight of the upper atmo&s;pherical Cylinder; the rea&s;on of which admi|rable power (according to their Suppo|&s;ition) is opened <HI>&s;upra cap.</HI> 5.</P>
<P N="3">3. And in as much as there runs down as weighty and potent aereal Cy|linders or Atmo&s;pherical portions by the &s;ides, as well as perpendicularly, therefore although the Marbles were not placed parallel to the Horizon, but vertically (as when each is drawn &s;eve|ral ways) this lateral pre&s;&s;ure of the At|mo&s;phere is as effectual to hold the Marbles together in that clo&s;e po&s;ture, as if they &s;tood parallel to the Horizon.</P>
<P N="4">4. And becau&s;e they will have a Salve for all Sores, although the&s;e En|gins be placed in a clo&s;e Gla&s;s-Receiver, whereby the aereal Columns, as well &s;uperior as inferior, are wholly inter|cepted by the interpo&s;ition of the great Gla&s;s Receiver, the Ela&s;ticity of the portion of Air included within that Gla&s;s Receiver, undertakes and effectu|ally performs the <HI>phaenomenon,</HI> by its vi|gorous
<PB N="255" REF="131">Ela&s;ticity or counterpre&s;&s;ion both upward, and downward, and late|rally, upon the included Marbles or He|mi&s;pheres.</P>
<P>And this is the Solution that now ob|tains among the <HI>Virtuo&s;i.</HI></P>
<P>And upon the&s;e premi&s;es there are ad|mirable trains of Philo&s;ophical Con&s;e|quences deduced with great indu&s;try and &s;ubtlety, in this particular in&s;tance of the Marbles, which a man may read at large in the late book of <HI>Hydro&s;tatical Experiments, Exp.</HI> 13, and el&s;ewhere.</P>
<P>And now for ought I know the mat|ter is brought to this i&s;&s;ue, whether this or the former Solution be the truer, (for I know not a third) and if this prove un|true or uneffectual, the former of the Vulgar Philo&s;ophy mu&s;t obtain, 'till &s;ome third be found out.</P>
<P>And therefore I will proceed in the examination of this new <HI>Hypothe&s;is.</HI></P>
<P>And although I think I have &s;aid e|nough again&s;t this whole Scheme of the Gravitation and Elatery of the Air, as it is propounded in the fourth, tenth, and eleventh Chapters; yet I &s;hall here add
<PB N="256" REF="132">&s;ome things more &s;pecifically applicable to the&s;e Engins and Experiments, and remit the Reader to tho&s;e Chapters, as to the general untruth of the entire <HI>hy|pothe&s;is.</HI></P>
<P>Fir&s;t therefore, as to the cohe&s;ion of the Marbles I offer the&s;e con&s;iderations:
1. It is plain, that the lower Mar|ble, if there were nothing el&s;e to &s;u&s;tain it but the recoiling Cylinder of Air im|pelling it upward, it would certainly fall to the Earth, notwith&s;tanding that imaginary <HI>potentia;</HI> for if it were other|wi&s;e, it would be a nece&s;&s;ary con&s;e|quence, that though it were not conti|guous to the upper, it would be &s;u&s;tai|ned by that <HI>potentia &s;u&s;tinens,</HI> and &s;o we &s;hould have Mil&s;tones floting in the Air, according to the fancy of the la&s;t men|tioned Author of Hydro&s;tatical Expe|riments.</P>
<P>But the help for this is, that in that in|&s;tance the impending &s;uperior column of Air being of equal &s;trength with the recoiling column of Air, there is an <HI>aequipondium</HI> between that <HI>pondus</HI> and <HI>po|tentia,</HI> and &s;o the &s;olute Marble or Mil|&s;tone,
<PB N="257" REF="132">having the advantage of his own weight, and the weight of the &s;uperior column would conquer the inferior; but here the inferior Marble is protected from the weight of the &s;uperior column of Air, and &s;o hath nothing but his own weight to contend with the infe|rior column, and its <HI>potentia,</HI> which lat|ter overmatcheth it, and &s;o keeps it &s;u&s;|pended.</P>
<P>But this will not cure the Sore; for &s;uppo&s;e it were two pieces of Wood, or that the Marbles were not excellently poli&s;hed, &s;o that they did not <HI>contingere in puncto,</HI> but &s;ome little fi&s;&s;ure or <HI>inter|&s;titia</HI> did let in any &s;mall portion of Air, the Marble would fall off; and yet there the lower Marble is protected from the impendent column of Air by the &s;upe|rior piece of Wood, or unpoli&s;hed Mar|ble as well as here.</P>
<P>And to &s;ay the&s;e little filaments of in|terpo&s;ed Air, which if all put together would not make a column of Air of a larger diameter than a &s;mall pin, &s;hould conquer the reflected Cylinder of Air, and its <HI>potentia,</HI> which the&s;e Ma&s;ters
<PB N="258" REF="133">&s;uppo&s;e to be equivalent in power to thirty, forty, nay one hundred pound weight, renders the whole Suppo&s;ition it &s;elf to be but utterly improbable. Some what therefore el&s;e it is, that keeps the lower Marble &s;u&s;pended to the up|per, and not the imaginary <HI>potentia</HI> of the reflected column of Air commen&s;u|rate to the <HI>area</HI> of the inferior marble.</P>
<P N="2">2. If the lower Marble were &s;u&s;tai|ned upon the account of the <HI>potentia &s;u|&s;tinens</HI> of the inferior column of Air, and by force thereof it could &s;u&s;tain (for in|&s;tance) forty pounds weight, &s;u&s;pended in the center of the Marble, it were not ea&s;ily conceptible how if but an eighth part of that weight were hanged near the limb or circumference of the lower Marble, it would fall a&s;under, as it will; for the <HI>potentia &s;u&s;tinens</HI> of the &s;ubjected column of Air is applied equally to all the <HI>area</HI> of the &s;ubjacent Marble. And the &s;eparation will follow, if the Mar|bles being oyled, the one may be &s;lided off from the other without any dif|ficulty; and then when they are &s;o &s;li|ded off, they are ea&s;ily thereby &s;evered,
<PB N="259" REF="133">becau&s;e no vacuity or in&s;tantaneous motion of the Air would follow there|upon: which could never be done, if they were &s;o &s;trongly wedged up one to another by &s;o &s;trong and powerful a counterpre&s;&s;ure of the reflecting column of Air, which pre&s;&s;eth up according to the new <HI>hypothe&s;is</HI> with a <HI>potentia</HI> able to &s;u&s;tain neer a hundred pound weight.</P>
<P N="3">3. <HI>Stevinus</HI> tells us in the ob&s;erva|tions upon the tenth Propo&s;ition of his Hydro&s;taticks, that if a ve&s;&s;el be made in the form of <HI>Fig.</HI> 17. with a hole in the bottom, and a piece of Wood lighter than Water, <HI>viz. B B.</HI> Cover that hole, and then let the ve&s;&s;el be filled with Water; as great a &s;trength will be required by the &s;tring at <HI>A</HI> to move that rundle of Wood from the hole it &s;tops, as if a weight of Water commen|&s;urate to the <HI>area</HI> of the rundle, from <HI>B</HI> to <HI>A,</HI> were impendent upon it. And this the Learned Author of Hydro&s;tatical Paradoxes avouches to have tried him|&s;elf, and yet the Water included is not an half nor a quarter of that weight of Water. And the column of Air that
<PB N="260" REF="134">the&s;e Ma&s;ters &s;uppo&s;e to pre&s;s the Water at <HI>A,</HI> can be no larger than the orifice of the Pipe at <HI>A,</HI> which is not one fifth part of the amplitude of the rundle <HI>B,</HI> nor of the hole which it &s;tops. But if there were &s;uch a reflected or recoiling column pre&s;&s;ing upward to the hole of the ve&s;&s;el and rundle that covers it, which is five times larger than the ori|fice at <HI>A,</HI> to let in a column of gravita|ting Air; this rundle, and the Water incumbent upon it, &s;hould be forcibly thru&s;t up by the recoiling column of Air: and yet Experience tells us, that it is &s;o far from being thru&s;t up by the <HI>po|tentia &s;u&s;tinens</HI> of the inferior aery co|lumn, that it is hardly to be rai&s;ed with|out difficulty by a Thrid.</P>
<P N="4">4. Again, take a ve&s;&s;el of Laton, of a cubical or cylindrical figure, about eight Inches diameter; make a round hole at the bottom of four Inches dia|meter. Then take a round piece of Bra&s;s or Lead, or &s;moothed Wood, of &s;ix Inches diameter, which may weigh two Ounces; wax it well, and exactly, and clo&s;ely cover the hole, that it may over|lap,
<PB N="261" REF="134">that no Air may go in or out by it, then rarifie the included Air, but not to a|ny con&s;iderable height, for then growing cold it will draw up the cover when clo|&s;ed. Then clo&s;e the top very clo&s;e with Laton and Soder, that no Air can get in; the Air I &s;uppo&s;e rarified may take up more room than its natural dimen&s;ion by about two &s;quare Inches, which is more than the dimen&s;ion of the Stopper: &s;o that the &s;uppo&s;ed Elatery of the Air hath no re&s;i&s;tence to its impelling up|ward, becau&s;e it hath room for its re|ception. I &s;ay that this Stopper will not be impelled up by the pre&s;&s;ure of the recoiling Cylinder of Air, though it weigh but two Ounces, and will be lif|ted up by a force or weight of three Ounces. And yet according to the&s;e mens Suppo&s;ition, this recoiling column hath a <HI>potentia</HI> to impell or keep up for|ty pound, nay an hundred pound weight, being commen&s;urate in power to an Atmo&s;pherical Cylinder of &s;ix Inches diameter, which according to their Suppo&s;ition mu&s;t weigh about 500l weight, namely a Cylinder of
<PB N="262" REF="135">Mercury of &s;ix Inches diameter, and twenty nine Inches high, <HI>viz.</HI> 783 &s;quare Inches of Mercury, which is near 500l weight. It is true I have not tryed this, but my ob&s;ervation of the third Ex|periment makes me little doubt of this.</P>
</DIV2>
<DIV2 N="18" TYPE="chapter">
<HEAD>CHAP. XVIII. <HI>Concerning the</HI> Magdeburgh <HI>Hemi&s;pheres, and their Cohe&s;ion, and the rea&s;on thereof.</HI></HEAD>
<P>THE Air is capable of ten&s;ion by force, and of rarifaction by heat; both which agree in this, that they both give a large expan&s;ion of a le&s;s portion of Air into a greater &s;pace than is natu|ral to it.</P>
<P>But herein they partly differ, and partly agree; that the immediate effect of a &s;trong ten&s;ion of Air by force (&s;uch as are the Air-pump, and the <HI>Magdeburgh</HI> Engin, and the <HI>Cacabus Evacuatorius</HI> de|&s;cribed by <HI>Shottus</HI> in his <HI>Technica curio&s;a, lib. 1. cap. 5. &amp; &s;equentibus</HI>) is attraction of the Superficies, to which the inclu|ded ten&s;ed Air is contiguous.</P>
<P>But the immediate effect of rarifaction
<PB N="263" REF="135">of the Air, which is performed by heat, is a laxation of the filaments of the Air at fir&s;t; for the Air being dilated, takes up more room, is more relaxed and ex|panded: but con&s;equentially there fol|lows a contraction as the heat decays, and the Air endeavours its re&s;titution to its natural texture, and &s;o endeavours its contraction, and con&s;equently lays hold on the contingent Superficies, within which it is impri&s;oned, and at|tracts it with its own contraction. The in&s;tances of both which motions and effects we have in the <HI>Magdeburgh</HI> He|mi&s;pheres de&s;cribed by <HI>Shottus, ubi &s;upra,</HI> and hereafter more fully explicated.</P>
<P><HI>Fig.</HI> 18, 19, 20. The Engin is thus de&s;cribed. Let there be two Brazen con|cave Hemi&s;pheres <HI>AB,</HI> with rings in the Poles or center of the convex Super|ficies of each of them at <HI>C</HI> and <HI>D,</HI> and a ring of Leather dipt in Wax to be placed between the two Hemi&s;pheres, <HI>viz. E,</HI> to keep the limbs or joints of them clo&s;e from admi&s;&s;ion of any Air between the commi&s;&s;ures or joints of the Hemi|&s;pheres; and a Stop-cock in the lower
<PB N="264" REF="136">Hemi&s;phere at <HI>E K,</HI> both the Hemi|&s;pheres conjoined with the Leather be|tween them. The&s;e Hemi&s;pheres thus joined, the Stop-cock at <HI>F</HI> to be left open, whereby in the <HI>Cacabus Evacuathius</HI> or <HI>Magdeburgh</HI> Engin, the Air in the cavi|ty of the Hemi&s;pheres may be as much exhau&s;ted as may be, and con&s;equent|ly that which remains being thereby put into a great ten&s;ion, to be inclo&s;ed by turning the Stop-cock, that no for|reign Air may be admitted. The&s;e He|mi&s;pheres thus ordered, will cohere &s;o &s;trongly together, that the &s;trength of many Hor&s;es will not &s;ever them, if the Hemi&s;pheres be large.</P>
<P>And the event is infallibly true, but the conte&s;t is touching the rea&s;on or So|lution of the <HI>phaenomena.</HI></P>
<P>The modern Philo&s;ophers, with <HI>Schot|tus</HI> in his fourth Book of his <HI>Technica cu|rio&s;a, cap. 7. &rsect; 3.</HI> (being now a Convert to the Gravitation of the Air) tells us, that the rea&s;on hereof is, that the weight of a column of Air impendent uppon the upper Hemi&s;phere, and the rever&s;e column of Air pre&s;&s;ing upon
<PB N="265" REF="136">the lower Hemi&s;phere upward, is the cau&s;e of this cohe&s;ion.</P>
<P>And that in ca&s;e the Hemi&s;pheres be not placed erect, but laterally, with their Poles parallel to the Horizon, the lateral pre&s;&s;ure of the two adver&s;e columns of Air perform the bu&s;ine&s;s, and keep them &s;trictly together again&s;t a mo&s;t powerful force indeavouring their &s;e|paration.</P>
<P>But &s;till with this caution, that the &s;eparating force work upon the centre of the Hemi&s;pheres, and &s;o draw upon all parts alike: for if the <HI>potentia &s;epa|rans</HI> be applied unequally, <HI>viz.</HI> at one &s;ide of each Hemi&s;phere, and not equally from the centre, then the &s;eparation will ea&s;ily follow upon the application of a &s;mall &s;eparating &s;trength, which is al&s;o mo&s;t certainly true. Again, if but a little portion of Air be let into the Stop-cock, the &s;eparation of them quickly follows, which is al&s;o true.</P>
<P>But now the vulgar Speculators think, that this Solution is untrue, and that the true rea&s;on of the cohe&s;ion of the&s;e Hemi&s;pheres is, becau&s;e that the
<PB N="266" REF="137">included portion of Air is not wholly exhau&s;ted, neither is it po&s;&s;ible by hu|mane power wholly to evacuate it. But a great part therereof is exhau&s;ted, and that which remains inclo&s;ed is un|der a very great and violent ten&s;ion, and hath a &s;trong natural <HI>conatus</HI> of re&s;titu|tion to its natural &s;taple and &s;tandard, and that the filaments of the Air lay hold upon every point of the concave Superficies, and draw them inward, as it endavours its own contraction.</P>
<P>That there is not, nor can be, any <HI>ca&s;ma</HI> or interval of empty &s;pace be|tween the convex Superficies of the in|cluded Air, and the concave Superficies of the including Hemi&s;pheres, for that is contrary to the common law of Na|ture; and yet the Air by its intrin&s;ick texture, and proper motion of re&s;tituti|on, to that ju&s;t dimen&s;ion that Nature hath a&s;&s;igned to it, affects its own con|traction to its own &s;tate, and with it draws together, and holds together the ambient body including it.</P>
<P>Not much unlike the ten&s;ion of Lute|&s;trings, highly wound up by their Pins,
<PB N="267" REF="137">which have a ten&s;ion and contraction of the extremes, to which they are fa&s;t|ned, namely the Bridg and the Pins.</P>
<P>That the rea&s;on why, if any Air be let in, even at a Pin-hole through the Hemi&s;pheres, it is greedily &s;ucked in by the ten&s;ed and &s;tretched Air, to relieve it from the Rack upon which it is &s;tretched, and being taken in it relieves that ten&s;ion, loo&s;eneth its contraction, and takes off its forcible attraction upon the concave Superficies of the including Hemi&s;pheres, and gives the included Air a fair relaxation to its due &s;ize, &s;ta|ple, and &s;tandard; and &s;o the cohe&s;ion cea&s;eth.</P>
<P><HI>Fig.</HI> 21. That the rea&s;on why an a|perture is ea&s;ily wrought, when the di|vul&s;ion is only of one &s;ide, is partly the &s;ame with the rea&s;on of the like divul|&s;ion of the the two cohering Marbles. 1. Becau&s;e the aperture is angular, and not all at once. 2. The aperture is <HI>cunei formis,</HI> which every body knows is more forcible than a parallel aperture. And 3. by this kind of angular opening the filaments of the Air are broken &s;uc|ce&s;&s;ively
<PB N="268" REF="138">one after another; but in a pa|rallel aperture all the filaments mu&s;t be broken at once, and &s;o make one com|mon re&s;i&s;tance to the force. As a piece of Cloth may be torn with ea&s;e by one man, when thrid is broken after thrid, but cannot be torn by four men, when all the thrids are &s;trained together, and &s;o have an united and uniform &s;trength and re&s;i&s;tance.</P>
<P>And they &s;ay, that although this En|gin is contrived with great pomp, yet in truth it is no more than that Experi|ment, which we practi&s;ed with our Nut&s;hels when we were children, where by clapping half a Nut&s;hel to our lips, or the back of our hands, and &s;uck|ing out the Air, they would &s;tick &s;o clo&s;e, that we could not ea&s;ily fillip them off.</P>
<P>The&s;e are the two rea&s;ons that con|tend for the Solution of this Experi|ment, the Gravitation of the Air or Atmo&s;phere of the one hand, and the <HI>motus</HI> or <HI>conatus re&s;titutionis</HI> of the Air, and the natural in&s;eparability of Bodies without any intervening Body of the
<PB N="269" REF="138">other hand. If the former be laid a&s;ide as untrue, the latter needs no great la|bour to prove it; for the&s;e be the only two Competitors for the Solution of this In&s;tance, that I ever heard of.</P>
<P>And I think it is very plain, that the imaginary gravitation of the Air, nei|ther hath nor can have any thing at all to do in this bu&s;ine&s;s.</P>
<P>And becau&s;e I had not tho&s;e Evacua|tory Engins before de&s;cribed, and if I had had them, yet I would not have &s;ingly re&s;ted upon them, without ma|king trial by rarifaction by heat, I took the method hereafter following, for the full examination of this In&s;tance.</P>
<P>For it is obvious beyond di&s;pute, that that if there be a cohe&s;ion wrought af|ter rarifaction of the Air by heat, in the In&s;tances hereafter given, as there is when there is a ten&s;ion of the Air by a forcible Evacuation, as in the former In&s;tance; the true cau&s;e of each cohe|&s;ion mu&s;t be one and the &s;ame. And if the <HI>pondus externi aeris</HI> contribute no|thing to the cohe&s;ion of the Hemi|&s;pheres after rarifaction of the included
<PB N="270" REF="139">Air by heat, it contributes as little to the cohe&s;ion of the Hemi&s;pheres forci|bly evacuated by an Air-pump, or the <HI>Cacabus Evacuatorius</HI> before mentioned.</P>
<P>And on the other &s;ide, if the cohe&s;ion of the Hemi&s;pheres after rarifaction by heat be cau&s;ed by the <HI>motus re&s;titutionis</HI> of the included rarified Air, and by the &s;trict continuity (as I may call it) of the filaments of the Air to the cavity of the Hemi&s;pheres, to avoid that Vacuity which would otherwi&s;e happen by the contraction of the Air into a le&s;s room than would fill the whole cavity; the &s;ame is unque&s;tionably the rea&s;on of the cohe&s;ion of the Hemi&s;pheres forcibly evacuated as above.</P>
<P>The In&s;tances therefore that I tryed are the&s;e that follow, which I &s;hall men|tion &s;everally, with my ob&s;ervation to each of them. For if I mi&s;take not, this one Experiment, duly improved, whol|ly &s;ets a&s;ide the imaginary Gravita|tion of the Air, &s;o u&s;ually applied to the Solution of the <HI>Torricellian</HI> Ex|periment, the cohe&s;ion of Marbles, the rai&s;ing of Water in Pumps, and
<PB N="271" REF="139">by Suction, and many more of like na|ture.</P>
<P>Fir&s;t, I cau&s;ed two Bra&s;s concave He|mi&s;pheres to be ca&s;t, each of &s;ix Inches and a quarter in the cavity, and about &s;even Inches diameter in the convexity, exactly clo&s;ing one to another on their rim, and the lower let up into the cavity of the upper about half an Inch, for their more exact clo&s;ure; and the outward rims of each about a quarter of an Inch in bredth, exactly clo&s;ing one upon another, &s;o that being clo&s;ed they made one perfect Sphere, according to the form of the <HI>Magdeburgh</HI> Hemi&s;pheres above de&s;cribed.</P>
<P>The lower Hemi&s;phere weighed &s;ix pounds, &s;even Ounces, and a half, <HI>viz.</HI> 103 Ounces, and half; the upper weigh|ed only &s;ix pounds.</P>
<P>I then took a circular piece of Calf|skin, a little above half an Inch broad, and in length &s;ufficient to compa&s;s the Hemi&s;pheres, and dipping it in melted Bees-Wax, with a very little Ro&s;in, &s;o that it might ju&s;t lye between the com|mi&s;&s;ures of the two Hemi&s;pheres, and
<PB N="272" REF="140">&s;top out all acce&s;s of the forreign Air be|tween them.</P>
<P>Fir&s;t therefore, without any thing more done, I applied the two Hemi|&s;pheres each to other, with the interpo|&s;ed girdle of waxed wet Leather, and pre&s;&s;ed them clo&s;e and hard together, that no commerce might be between the included and the common Air.</P>
<P>And &s;o there neither was nor could be any force of compre&s;&s;ion u&s;ed to the included Air, becau&s;e 'till the clo&s;ure of the. Hemi&s;pheres it had a free inter|cour&s;e with the external Air, and when perfectly clo&s;ed it was but ju&s;t as much as the Hemi&s;pheres would freely con|tain, and con&s;equently of the &s;ame tex|ture with the forreign Air.</P>
<P>In this In&s;tance, the upper Hemi|&s;phere rai&s;ed gently by the ring, there &s;eemed a little weak cohe&s;ion be|tween them, becau&s;e the rims were per|fectly clo&s;ed, and the &s;eparation was altogether in the &s;ame moment, but the cohe&s;ion &s;o faint and weak, that it would not &s;u&s;tain the hundredth part of the weight of the lower Hemi&s;phere, and &s;carce perceptible.</P>
<PB N="273" REF="140">
<P>And the rea&s;on of the di&s;parity be|tween the cohe&s;ion of the&s;e Hemi|&s;pheres, and that before mentioned of the 2 poli&s;hed Marbles, are the&s;e. 1. Be|cau&s;e the contiguity of the two po|li&s;hed Marbles is in all points of their Superficies, but here the contiguity of the rims of the Hemi&s;pheres was but in a circle of a quarter of an Inch broad, and &s;o the forreign Air had a &s;horter journey to go in the moment of the &s;e|paration of the Hemi&s;pheres, than in the moment of the &s;eparation of the poli|&s;hed Marbles. 2. Becau&s;e the contigu|ity of the poli&s;hed Marbles is without any interpo&s;ition of Leather, which po&s;&s;ibly would impede the firmne&s;s of the cohe&s;ion of the two Marbles them|&s;elves.</P>
<P>But now if the pre&s;&s;ure of the aereal Cylinders either in the poli&s;hed Mar|bles, or in the in&s;tances of the Hemi|&s;pheres, before and hereafter given, were the cau&s;e of their cohe&s;ion, what imaginable rea&s;on can be given why the&s;e two Hemi&s;pheres &s;hould not co|here as firmly in this In&s;tance.</P>
<PB N="274" REF="141">
<P>For though there be Air included be|tween the two Hemi&s;pheres, yet all communication between the included and forreign Air is perfectly excluded by walls of Bra&s;s, and the impervious Leather girdle.</P>
<P>If it be &s;aid, that the Ela&s;ticity of the included Air re&s;i&s;ts the compre&s;&s;ion by the forreign Air, and &s;o impedes the cohe&s;ion.</P>
<P>I &s;ay if any &s;uch Ela&s;ticity were ad|mitted in the Air, (which I do not) yet mo&s;t certainly the included Air hath no greater Ela&s;ticity than the common Air, whereof it was but ju&s;t now a por|tion, and hath received no more com|pre&s;&s;ion by the juncture of the Hemi|&s;pheres, no more than Air in a Bottle covered with a flat Board or Paper.</P>
<P>The con&s;equence whereof is, that the Ela&s;ticity of the forreign Air is as &s;trong as the Ela&s;ticity of the included Air, and mu&s;t needs keep it in <HI>aequilibrio.</HI> And the con&s;equence thereof is, that if the <HI>pon|dus externi aeris</HI> (if it were any way con|&s;iderable) would have its free exerci&s;e upon the&s;e Hemi&s;pheres, though filled
<PB N="275" REF="141">with Air; for according to the&s;e Ma|&s;ters &s;uppo&s;ition, the Cylinder of Air of each &s;ide pre&s;&s;ing each Hemi&s;phere, is above &s;even hundred pound weight, which it may freely exerci&s;e, the imagi|nary Ela&s;ticity of the included and for|reign Air being <HI>ex &s;uppo&s;itione</HI> equal. But the en&s;uing Experiments will ren|der this more evident.</P>
<P>Secondly therefore, I took a handful of flax, and leaving the mouth of the lower Hemi&s;phere upward, I put in the flax, and gave fire to it, holding the up|per Hemi&s;phere clo&s;e over it, whereby the Air in both was greatly rarified, and a con&s;iderable portion of the &s;pace taken up by the flame of the flax. Then clapping the upper Hemi&s;phere upon the lower, with the interpo&s;ed Leather girdle, I pre&s;&s;ed them together with all the &s;trength I had, neither were they po&s;&s;ibly capable of a neerer or clo&s;er contiguity to the interpo&s;ed Leather, though the imaginary Cylinder of the Atmo&s;phere had pre&s;&s;ed them, and hereupon the flame and fire was pre|&s;ently extingui&s;hed.</P>
<PB N="276" REF="142">
<P>The Events were as followeth.</P>
<P N="1">1. There grew a pre&s;ent cohe&s;ion of the two Hemi&s;pheres together, even while they were hot, and the included Air under a high degree of rarifaction by the heat, and &s;o could not have any con&s;iderable ten&s;ion while the heat con|tinued.</P>
<P>And the rea&s;on of this cohe&s;ion was plainly this. That the fire and flame had not only rarified the Air included within the compa&s;s of the Hemi&s;pheres, to an expan&s;ion far greater than was na|tural to it; but al&s;o the flame and fire took up a con&s;iderable portion of the &s;pace between the Hemi&s;pheres, which being extinct in the moment of their juncture, that very rarified Air that was within, was forced to take up &s;o much more &s;pace as the flame took up before its extinction. And from thence grew nece&s;&s;arily an attraction upon the cavity of the Hemi&s;pheres, though that very Air was under a rarifaction by the con|tinuing heat.</P>
<P N="2">2. But this cohe&s;ion was but weak, becau&s;e the Air was then under a
<PB N="277" REF="142">&s;trong dilatation by the continuing heat, and therefore the upper Hemi|&s;phere lifted up by the ring, would not &s;u&s;tain the weight of the lower Hemi|&s;phere.</P>
<P N="3">3. But when the Hemi&s;pheres thus hea|ted, and the included Air greatly rari|fied thereby, were permitted to conti|nue together clo&s;ed 'till they were per|fectly cold, and thereby the Air had op|portunity to contract it &s;elf, or at le&s;t to endeavour it as much as it could. Now the cohe&s;ion of the Hemi&s;pheres grew &s;trong, &s;o that the upper lifted up would rai&s;e the lower in conjunction with it, with the addition of &s;ome weight appended to the lower ring. And the rea&s;on was, becau&s;e the heat which was the cau&s;e of the great dilata|tion of the included Air was now cea|&s;ed, and the Air by its motion of re|&s;titution endeavoured to contract it &s;elf to its natural Expan&s;ion.</P>
<P>And becau&s;e the included Air (it may be) was expanded to above four times its true natural &s;ize and dimen&s;ion, and now endeavoured to contract it &s;elf
<PB N="278" REF="143">into that &s;pace, but could not attain it, unle&s;s three fourths of the &s;pace inclu|ded within the Hemi&s;pheres &s;hould have been left perfectly empty, the Air en|deavouring its contraction, according to the particular inclination of its own motion; yet by the common law of the Univer&s;e was kept under its former Expan&s;ion, to prevent the <HI>ca&s;ma</HI> be|tween the Air and the concave Super|ficies of the Hemi&s;pheres, and &s;o as much as was po&s;&s;ible attracted upon them, and kept them together, no for|reign Air being admi&s;&s;ible for the relief of the included Air, to help to re&s;tore it to its due &s;ize and texture: as a living Oy&s;ter contracts its &s;hell together by its own contraction within its &s;hell, when a per&s;on is opening in. The compari|&s;on is homely, and &s;uits not in all things, becau&s;e the Oy&s;ter is a vital Being, but yet it &s;erves to explicate the method of this attraction, by the filaments of the Air upon the contiguous concave Superficies.</P>
<P>And from this in&s;tance of fired flax (re&s;embling very much the common
<PB N="279" REF="143">in&s;tance of Cupping-gla&s;&s;es,) it ap|pears plainly, that in tho&s;e Gla&s;&s;es the fle&s;h is not driven up by pre&s;&s;ure of the forreign Air upon the gla&s;s or the con|tiguous parts of the fle&s;h; but purely by the attraction of the included re&s;idue of Air upon the extinction of the flame. For the Hemi&s;pheres were at fir&s;t pre&s;|&s;ed together as clo&s;e as they could be, and no man can imagine that the exter|nal Air can have any influence through the&s;e Brazen Walls, that are neer half an Inch thick, where yet the Attraction upon the included Superficies is vi&s;ible and apparent; and in this and my other Experiments it was not po&s;&s;ible for the Hemi&s;pheres to receive a greater or clo|&s;er contiguity than I gave them on their fir&s;t union: and therefore I do not wonder, that <HI>Schottus,</HI> though too ha&s;ti|ly &s;ub&s;cribing to the pre&s;&s;ure of the Air, as a Solution of &s;ome Experiments, yet in his <HI>Technica Curio&s;a, l. 4. cap.</HI> 12. &sect; I. is forced to confe&s;s <Q><HI>carnem &amp; &s;anguinem &s;ub|intrare cucurbitas, nec pre&s;&s;ione Aeris ex|terni carni circum illas incumbenti, nec pre&s;&s;ione aeris illas incumbentis &amp; depri|mentis,
<PB N="280" REF="144">ac intra carnem mergentis, &s;ed &s;uctione &amp; attractione.</HI></Q></P>
<P N="3">3. Becau&s;e I would improve the Ex|periment to the uttermo&s;t, I made a try|al with a &s;tronger heat. I therefore put burning Coals and red hot Iron into each Hemi&s;phere, 'till they were hot as I could well touch them, and then ca|&s;ting out the Coals, the Air within the cavity of each Hemi&s;phere was highly rarified; then clapping the Leather gir|dle about the rim I clo&s;ed the Hemi|&s;pheres very clo&s;e, as my &s;trength could force them together; the Events where|of were the&s;e:</P>
<P N="1">1. While the Hemi&s;pheres were hot, and &s;o the included Air under a high degree of rarifaction, there was very little or no cohe&s;ion, for the Air was under the &s;ame laxation as at fir&s;t, and therefore they would pre&s;ently fall a&s;under, the upper being rai&s;ed by the ring.</P>
<P N="2">2. As the heat decayed, and the He|&s;pheres grew gradually colder and col|der, and con&s;equently the Air more and more endeavours to contract it &s;elf, and
<PB N="281" REF="144">as a con&s;equence thereof attracted more forcibly upon the cavity of the Hemi|&s;pheres, the &s;tronger was there cohe|&s;ion; becau&s;e as the Air grew colder, it endeavoured more and more to ac|quire its ju&s;t natural dimen&s;ion and tex|ture.</P>
<P N="3">3. At la&s;t, when the heat was quite extinct, and the Hemi&s;pheres grown perfectly cold, the cohe&s;ion was &s;o &s;trong, that the upper Hemi&s;phere &s;u&s;|pended upon a hook, did not only &s;u|&s;tain the lower Hemi&s;phere, which weighed neer &s;even pounds, but al&s;o a weight of twenty eight pounds more, in all about thirty five pound weight, before they would be disjoyned.</P>
<P>For now the Air being di&s;charged of that heat that kept it laxe, and without a bent, or ten&s;ion, or contraction in|ward, did now endeavour its contra|ction &s;trongly, and therewith pulled inward the Hemi&s;pheres, from which it could not be &s;evered, by rea&s;on of common Natures declination of a Va|cuity.</P>
<P N="4">4. My fourth Tryal was this, that
<PB N="282" REF="145">when the Hemi&s;pheres were fir&s;t hea|ted, and clapt together, and thereby when they became cold, cohered excee|ding &s;trongly; yet when they were un|der that &s;trong cohe&s;ion, that they would &s;u&s;tain a con&s;iderable weight as before, without parting a&s;under, yet if afterwards they were brought but to a moderate heat, either by a chafing-di&s;h of Coals put under them, or by holding them neer the fire, they would &s;uddenly fall a&s;under of them&s;elves, without any weight appended to &s;ever them.</P>
<P>The rea&s;on whereof is apparent, namely that by the heating of the He|mi&s;pheres the included Air is again ex|panded, and its ten&s;ion laxed, and the filaments thereof which were before under a ten&s;ion and contraction by the Air, &s;triving to gain its natural tempe|rament, are now let loo&s;e, as a Lute|&s;tring is let down by the un&s;crewing of the Pins. And con&s;equently the &s;uction and attraction of the Air upon the con|cave Superficies of the Hemi&s;pheres, which before held them together, is re|laxed and di&s;charged.</P>
<PB N="283" REF="145">
<P>And thus we have the true <HI>phaenome|na</HI> of this Engin, and, as I take it the true rea&s;on and &s;olution of them.</P>
<P>And upon the&s;e In&s;tances I do con|clude,</P>
<P N="1">1. That men have had very little rea&s;on to conclude the Gravitation or Pre&s;&s;ure of the Air upon the inferior World, or the parts thereof; for the co|he&s;ion of the&s;e Engins is mo&s;t plainly upon another rea&s;on, as appears by what is before declared.</P>
<P N="2">2. That this in&s;tance is &s;o far from concluding the Gravitation of the Air in that mea&s;ure, that the late Ma&s;ters contend, that plainly that Suppo&s;ition neither hath nor can have to do in the &s;olution of the&s;e In&s;tances.</P>
<P>For mo&s;t unque&s;tionably, the Air doth as much gravitate (if at all) upon the Hemi&s;pheres, when the included Air is rarified by heat, in the&s;e In&s;tan|ces, as it doth when the Hemi&s;pheres are grown cold; and yet in the former ca&s;e there is no cohe&s;ion, but contrari|wi&s;e a &s;eparation of the cohering He|mi&s;pheres if again they are heated.</P>
<PB N="284" REF="146">
<P N="3">3. That the cau&s;e of the cohe&s;ion therefore is not <HI>ab extra,</HI> or <HI>de foris,</HI> but <HI>ab intra;</HI> namely, one &s;pecifical to the Air, whereby becoming cold after a great expan&s;ion by heat, it endeavours its contraction to its due &s;pace and tex|ture, by a motion of re&s;titution; the o|ther common to all parts of the Uni|ver&s;e, that common law of Nature that pre&s;erves contiguity, or indeed rather continuity of the parts of the Univer&s;e: and therefore &s;uffers not the Air to con|tract it &s;elf, &s;o as to leave an empty &s;pace between it &s;elf and the concave of the Hemi&s;pheres, whereby it comes to pa&s;s, that the Air endeavouring to contract it &s;elf, layes hold upon, and endeavours to contract and hold together all parts whereunto it is contiguous, when no acce&s;s of forreign Air is admitted.</P>
<P N="4">4. That the lea&s;t admi&s;&s;ion of for|reign Air, though through a Pin-hole, in the Hemi&s;pheres, gradually gives a relaxation of the ten&s;ion of the included Air, which greedily &s;ucks it in, and thereby is delivered gradually from its ten&s;ion, and lets go its hold of the conti|guous
<PB N="285" REF="146">Superficies, which is the natural and nece&s;&s;ary effect of that ten&s;ion.</P>
<P>I cannot ea&s;ily perceive how the&s;e Conclu&s;ions again&s;t the imaginary Gra|vitation of the Air can be evaded.</P>
<P>If it &s;hould be &s;aid, that the rea&s;on why the Hemi&s;pheres cohere not when they are hot, is, becau&s;e the convexity likewi&s;e of the Hemi&s;pheres are al&s;o hot, and &s;o retund the Gravitation or Pre&s;|&s;ure of the Air upon them by their heat, which is not &s;o done when they are cold.</P>
<P>I an&s;wer 1. That though the con|vex Superficies were admitted to be as hot as could be indured, yet the Sphere of that Activity is not two foot in cir|cumference, which could never break the pre&s;&s;ure of a column of Air of at lea&s;t &s;even Miles high, and near a thou&s;and pound weight, according to the Sup|po&s;ition. 2. Neither is the heat requi|red to make &s;uch a disjunction of that Extremity, as to make any &s;uch impre&s;|&s;ion upon the Air; for if the Hemi|&s;pheres be made but bloud warm after their cohe&s;ion, they will fall a&s;under.</P>
<PB N="286" REF="147">
<P N="3">3. But wholly to prevent this imagina|tion, if the Hemi&s;pheres be ca&s;ed over with a flat or &s;pherical Cover of Wood, Lead, or Bra&s;s, which may receive the &s;uppo&s;ed Gravitation of the Air, yet the cohe&s;ion, while the air is hot within, will not la&s;t; for it is the laxation or rela|xation of the ten&s;ion of the Air within that, gives the &s;eparation, or ea&s;ie &s;epa|rability of the Hemi&s;pheres.</P>
</DIV2>
<DIV2 N="19" TYPE="chapter">
<HEAD>CHAP. XIX.</HEAD>
<HEAD TYPE="sub"><HI>Concerning the rai&s;ing of the Water by Pumps or Syringes, and the Cau&s;e thereof.</HI></HEAD>
<P>IN the two former Chapters I have con&s;idered the cohe&s;ion of poli&s;hed Marbles, and the <HI>Magdeburgh</HI> Hemi|&s;pheres, both in truth re&s;ting upon So|lutions &s;omewhat of the &s;ame nature. And therein I have as I think excluded the Gravitation of the Air, or Atmo|&s;phere, or aereal Cylinders, from any contribution thereunto.</P>
<P>I have cho&s;en in this Chapter to con|&s;ider
<PB N="287" REF="147">the Elevation of Water in Pumps and Syringes, both which are in truth but the &s;ame Engin, though circum|&s;tantially varied.</P>
<P>And although I &s;hall herein have oc|ca&s;ion to &s;ay &s;omething touching the Gravitation of the Air, and &s;hall in &s;ome mea&s;ure evidence, that the Water is not rai&s;ed in the&s;e Engins by the weight of the Air, pre&s;&s;ing upon the re&s;tagnant Well or other ve&s;&s;el of Water, yet I &s;hall not labour that, much, in this di&s;|qui&s;ition, becau&s;e enough hath been &s;aid thereof before.</P>
<P>But my principal &s;cope herein is to di&s;cover, even to &s;en&s;e, that there is no &s;uch Ela&s;ticity in a &s;eparate portion of common Air as the Elateri&s;ts &s;uppo&s;e, whereby to &s;alve the &s;u&s;pen&s;ion of a co|column of twenty nine Inches of Mer|cury in the <HI>Torricellian</HI> Experiment, when the &s;ame is pent up in a clo&s;e ve&s;|&s;el or room, every where excluding the imaginary pre&s;&s;ure of the Atmo&s;pheri|cal Cylinder; and con&s;equently that the Solution of that Experiment, either by the Weight or by the Spring of the
<PB N="288" REF="148">Air, is a mi&s;taken Solution, and hath no reality in it.</P>
<P>The rai&s;ing of Water by common Pumps or Syringes (e&s;pecially as it is this day ordered, &s;ometimes with dou|ble, &s;ometimes with &s;ingle Valves, to hinder the regre&s;s of the Water) is &s;o well known even to ordinary Plum|mers, that it needs no accurate de&s;crip|tion.</P>
<P>But the rea&s;on of this Elevation of the Water is variou&s;ly rendred, accor|ding to the different <HI>hypothe&s;es</HI> that men have entertained.</P>
<P>The ancient and common, and I think the true rea&s;on thereof, is this:</P>
<P>The lower end of the cavity of the Pump or Syringe being immer&s;ed below the Superficies of the re&s;tagnant Water, there is a Cylinder of Air in the cavity of the Pump or Syringe, between the Superficies of the Water and the bottom of the Bucket and upper Valve of the Pump, or between the Superficies of the Water, and the bottom of the <HI>Em|bolus</HI> of the Syringe clo&s;ely penned up.</P>
<P>That by the Elevation of the Bucket
<PB N="289" REF="148">in the Pump, or <HI>Embolus</HI> in the Syringe, that portion of intermediate Air is un|der a ten&s;ion, and draws vigorou&s;ly upon the Superficies of the re&s;tagnant Water, and that again upon the conti|guous Water, and &s;o the ten&s;ed <HI>funicu|lus</HI> of the Air rai&s;eth a <HI>funiculus</HI> of Wa|ter, commen&s;urate to the cavity of the Pump or Cylinder, which again by depre&s;&s;ion of the Bucket ri&s;eth through the Leather-valve that covers it, and by an iterated elevation of the Bucket or <HI>Embolus</HI> draws up more, whereby there is a continued &s;upply of a <HI>funiculus aque|us,</HI> which is finally thrown out at the orifice, or no&s;e of the Pump.</P>
<P>That it is a certain truth, that Water is rai&s;ed either by a <HI>pondus</HI> or pre&s;&s;ure, that is equivalent to the weight of the Water that is elevated, as in the Engins where Forcers or pre&s;&s;ures are u&s;ed to rai&s;e Water; or el&s;e by an attractive <HI>potentia</HI> equal to the weight of the Wa|ter drawn up, as in Pumps and Syrin|ges.</P>
<P>That con&s;equently, the <HI>vis</HI> or <HI>potentia &s;uctoria</HI> or <HI>attractiva,</HI> will rai&s;e &s;uch a
<PB N="290" REF="149">weight of Water as is le&s;s than this <HI>vis</HI> or <HI>potentia,</HI> (for whether the Elevation of Water be by a <HI>vis deprimens</HI> as in pre&s;&s;ing Engins, or <HI>vis &s;uctoria</HI> or <HI>attra|ctiva</HI> as in Pumps or Syringes, or the preponderation of the <HI>potentia</HI> to the weight of the Water) thus it &s;u&s;tains, imples, or attracts, and therefore they are all reducible to the rea&s;on of the <HI>libra</HI> or Ballance.</P>
<P>And on the other &s;ide, if the weight of the Water exceed the <HI>pondus</HI> or <HI>poten|tia</HI> which mu&s;t rai&s;e it, it cannot either draw, or impell, or keep it up beyond an <HI>aequilibrium</HI> with that <HI>pondus</HI> or <HI>potentia impellens</HI> or <HI>attrahens.</HI></P>
<P>And therefore if there be an exce&s;|&s;ive di&s;tance between the Superficies of the re&s;tagnant Water, and the bottom of the <HI>Embolus</HI> or Bucket, &s;uppo&s;e it 50 or 60 foot of perpendicular height, whereby the <HI>potentia attractiva</HI> is over|matched with a <HI>pondus</HI> of Water more than its &s;trength, it will not rai&s;e it to a due height. For &s;till as I &s;aid, where any weighty body is rai&s;ed out of its place, it mu&s;t be by a greater weight, or
<PB N="291" REF="149">at le&s;t by a <HI>potentia,</HI> exceeding that weight of the Body to be rai&s;ed.</P>
<P>But the modern Philo&s;ophy tells us, that the rai&s;ing of the Water in the Pump or Syringe, is not by a <HI>vis attra|ctiva</HI> or <HI>&s;uctoria</HI> of the Bucket or <HI>Embolus,</HI> but that it is forced up by the weight of a Cylinder of Air, commen&s;urate to the cavity of the Pump or Syringe.</P>
<P>And that the Elevation of the Pump or <HI>Embolus</HI> of the Syringe, attenuating the Air inclo&s;ed in the cavity of the Pump or Syringe, and thereby di&s;abled by its laxity to re&s;i&s;t the pre&s;&s;ure of the external Cylinder of atmo&s;pherical Air, the Water is driven up into the cavity of the Pump or Syringe.</P>
<P>And becau&s;e a Cylinder of Mercury of twenty nine Inches and half, is by them &s;uppo&s;ed to be of equal weight to the Cylinder of Air of like diameter, reaching from the top of the Atmo|&s;phere unto the ve&s;&s;el of re&s;tagnant Mercury in the <HI>Torricellian</HI> Experiment, and a Cylinder of <HI>Mercury</HI> of twenty nine Inches and half high, countervails in weight a Cylinder of Water of like
<PB N="292" REF="150">diameter of about thirty three foot high, and con&s;equently a Cylinder of the At|mo&s;phere counterpoi&s;eth a Cylinder of Water of about thirty three foot high, therefore the Water in a Pump will be rai&s;ed but ju&s;t to that height, <HI>viz.</HI> neer thirty three foot, and no higher, becau&s;e &s;uch a column or Cylinder of Water is counterpoi&s;ed by an Atmo&s;pherical Cylinder of like diameter. Thus I think it is rendred by <HI>Schottus</HI> in his <HI>Technica Curio&s;a, l.4.cap.8.&sect;.4.</HI> and by the Excellent Author of <HI>Hydro&s;tatical Para|doxes, n.5.</HI> and by other learned men of this latter age.</P>
<P>But under their favour I think this is not the true Solution of the in&s;tance in hand, but the fir&s;t is the true Solution thereof.</P>
<P>If the elevation of the Water in the Pump may be more con&s;iderably higher than 33 foot, certainly this latter Solution cannot &s;erve. And though this po&s;&s;ibly hath not been fully tryed, and requires exact Engins to effect the Tryal to the uttermo&s;t; yet there are many that do experimentally affirm,
<PB N="293" REF="150">that a Pump or Syringe well ordered will rai&s;e Water above forty foot perpendi|cular height; and if &s;o, the counterpoi&s;e of the aereal Cylinder will not do the bu&s;ine&s;s. But this I have not tryed, I will therefore apply my &s;elf to what I have tryed.</P>
<P><HI>Fig.</HI> 22. I took therefore a great and &s;trong globular gla&s;s Bottle, <HI>ABC,</HI> holding five Quarts of Water, of about nine Inches Diameter, with a double orifice, <HI>viz.</HI> one at <HI>A,</HI> wherein to fa|&s;ten my Pump hereafter de&s;cribed, ano|ther at <HI>B,</HI> to let in or pour out Water, to leave open or clo&s;e, as I &s;aw cau&s;e.</P>
<P>In <HI>A</HI> the neck of the Bottle I fa&s;tned a Laton Pump or Syringe, or about an Inch and a half diameter, marked <HI>D,</HI> with a &s;mall Pipe about half an Inch di|ameter; reaching neer the bottom of the Gla&s;s, <HI>viz. E;</HI> an <HI>Embolus</HI> at <HI>G</HI> reach|ing down neer <HI>H,</HI> and a little crooked Pipe at <HI>H</HI> to drive out the Water by the depre&s;&s;ion of the <HI>Embolus.</HI></P>
<P>This Pump was fa&s;tned and &s;trongly luted in the neck of the Gla&s;s with a double Valve, one about <HI>A</HI> to receive the
<PB N="294" REF="151">Water into the Pump, and to &s;u&s;tain it from returning, by depre&s;&s;ing the <HI>Embolus,</HI> another at <HI>K</HI> the top of the orifice, to keep the Air from entring upon rai&s;ing the <HI>Embolus.</HI></P>
<P>So that now the Bottle was the Well, which I filled up with Water.</P>
<P>Therefore leaving open the orifice at <HI>B,</HI> whereby the Air had free acce&s;s into the Bottle, by lifting up and depre&s;&s;ing the <HI>Embolus G</HI> the Water was freely and ea&s;ily without any difficulty drawn out at the orifice <HI>K,</HI> through the Valve there placed, and &s;o I emptied half the Bottle of Water, namely to <HI>I</HI> the &s;upe|rior half, being full of free uncompre&s;|&s;ed and common Air; and the lower half at <HI>I</HI> being full of Water.</P>
<P>The Pump being in this po&s;ture, I took a &s;hort piece of Cork, fir&s;t boyled and then dipt in melted Bees-wax and Ro&s;in with it, I clo&s;ely luted up the ori|fice at <HI>B,</HI> &s;o that no air could po&s;&s;ibly en|ter. And then I lifted up and depre&s;&s;ed the <HI>Embolus</HI> &s;everal times, &s;o long 'till I could &s;ee the whole &s;ucce&s;s of this Tryal.</P>
<P>Fir&s;t, the <HI>Embolus</HI> was rai&s;ed, but not
<PB N="295" REF="151">with equal facility, as it was done when the orifice <HI>B</HI> was open.</P>
<P>The rea&s;on whereof is, becau&s;e every elevation of the <HI>Embolus</HI> gave a violent ten&s;ion to the Air in the &s;uperior cavity of the Gla&s;s, which upon every portion of Water drawn up mu&s;t nece&s;&s;arily be expanded into a larger &s;pace to &s;upply the &s;pace left by the rai&s;ed Water. So that the expan&s;ion of the Air was not natural, or of its own accord, but by a violent attraction wrought upon it, and ten&s;ion of it.</P>
<P>Secondly, yet notwith&s;tanding the exclu&s;ion of the Air, I did freely pump out above a quart of Water, whereby the Water &s;ub&s;ided an Inch and a half below <HI>I,</HI> and con&s;equently the Air ex|panded and dilated to &s;o much more &s;pace than it had before, <HI>viz.</HI> whereas the &s;uperior cavity of the Gla&s;s held by the Air was two quarts and half, now it took up the room of three quarts and half, and &s;omewhat more.</P>
<P>So that here was a quart of Water rai&s;ed up by the &s;uction of the <HI>Embolus,</HI> and yet no po&s;&s;ible Gravitation of that
<PB N="296" REF="152">imaginary atmo&s;pherical column to pre&s;s or drive it up; &s;o that &s;urely the a&s;cent of the Water in the Pump is not by the Ballance, <HI>aequipondium,</HI> or pre|ponderation of a column of the Atmo|&s;phere to the column of Water rai&s;ed in the cavity of the Pump, for here was no acce&s;s for any &s;uch column: whe|ther the imaginary Ela&s;ticity of the in|cluded portion of Air may be called in to help the matter, we &s;hall &s;ee here|after.</P>
<P>Thirdly, but when I had rai&s;ed up this quart of Water, and emptied &s;o much out of my Bottle, all my iterated tractions and tru&s;ions of my <HI>Embolus</HI> could rai&s;e not one drop more.</P>
<P>But all that was done by the&s;e repea|red motions, was only the rarifying of the Air included in the Pump, when the <HI>Embolus</HI> was lifted up, and conden|&s;ing it again as the <HI>Embolus</HI> was depre&s;|&s;ed, but no Water rai&s;ed.</P>
<P>Now in this in&s;tance, the rea&s;on why a quart of water was rai&s;ed, though the orifice at <HI>B</HI> were &s;topped, was be|cau&s;e the <HI>potentia &s;uctoria</HI> or <HI>attractiva</HI>
<PB N="297" REF="152">of the Pump was &s;trong enough to give a dilatation of the Air to a greater &s;pace by a quart than it had before.</P>
<P>And the rea&s;on why it could rai&s;e no more, is this, namely, in as much as every portion of Water rai&s;ed out of the ve&s;&s;el, mu&s;t of nece&s;&s;ity leave a &s;pace devoid of &s;o much Water as is &s;o rai&s;ed up, and that derelicted &s;pace mu&s;t ei|ther be wholly vacant of any Body, which by the univer&s;al law of the Uni|ver&s;e is prohibited, or el&s;e the Air mu&s;t expand it &s;elf to fill it. And in as much as the Air having undergone as great an Expan&s;ion already (by the evacuati|on of the fir&s;t quart of Water) as this <HI>potentia</HI> or <HI>vis attractiva</HI> was able to effect. The included Air thus expanded re&s;i&s;teth any further expan&s;ion with an equal &s;trength to the attractive power of the Pump, and &s;o renders it <HI>conamen irritum,</HI> to give it a larger expan&s;ion, and con&s;equently no more Water is rai&s;ed.</P>
<P>But if a greater &s;trength were applied, &s;trong enough to ma&s;ter that re&s;i&s;tence, as if the Pump were longer, that it
<PB N="298" REF="153">might give a &s;tronger &s;uction, that might overmatch the re&s;i&s;tence of the included Air again&s;t a higher degree of ten&s;ion; yea or if the &s;uperior Air, af|ter this quart of Water was evacuated, had a &s;trong external heat applied to it, whereby it might be capable of a larger expan&s;ion, the Water (while the Air was under this forcible expan&s;ion) would be as ea&s;ily rai&s;ed by the Pump as at fir&s;t. But this I dur&s;t not try, for fear of breaking my Gla&s;s, or unluting of it.</P>
<P>Upon this con&s;ideration and tryal it is manife&s;t,</P>
<P>Fir&s;t, that the Gravitation or pre&s;&s;ure of the external Air is not the cau&s;e of rai&s;ing the Water in the Pump; for here it is rai&s;ed where there is no Gravi|tation, the orifice at <HI>B</HI> being perfectly &s;topt.</P>
<P>Secondly, that the common Air hath no &s;uch Ela&s;ticity, as the modern Phi|lo&s;ophy a&s;&s;igns to it; for here a portion of Air included in the Gla&s;s is of the &s;ame texture with the common Air, and a portion of it, and yet evidently there
<PB N="299" REF="153">is no &s;uch Ela&s;ticity in it as is &s;uppo&s;ed.</P>
<P>And this appears, 1. becau&s;e it is not expanded to one third part of greater &s;pace than it had before, without a force offered to it, as above is &s;hewn. 2. When it is expanded to a third part of &s;pace more than it had, it is &s;o far from a na|tural expan&s;ion of it &s;elf farther, that it refi&s;ts the <HI>attractiva potentia</HI> of the Pump to give any larger expan&s;ion. And 3. if it had yet a natural expan&s;ive power without force or violence added to it, it would certainly drive up the re&s;t of the Water that remains, e&s;pecially when the Air in the Pump is rarified or extended by the elevation of the <HI>Embo|lus,</HI> and yet no Water follows it, in this in&s;tance, which yet it would do, if the Air had a continuing Spring or Ela&s;ti|city to drive it up.</P>
<P>It is true, that naturally all the &s;paces of this lower World (at le&s;t) are and mu&s;t be filled with &s;ome body or other: and as one body moves or is moved out of one &s;pace to another, &s;ome other body &s;ucceeds in that &s;pace that is &s;o left, and fills it. And the fluid Bodies of Air and
<PB N="300" REF="154">Water, or &s;ome fluid bodily &s;ub&s;tance, equivalent to either of them, are in re|&s;pect of their fluidity fitted more than other &s;olider Bodies, to &s;upply and make good the <HI>inter&s;titia</HI> of other Bodies; and if they be contiguous unto them, to &s;lip into the &s;paces de&s;erted by their motion into other &s;paces, and accordingly will do it, if they are not impeded by the re|&s;i&s;tance or interpo&s;ition of other more &s;tubborn and untractable Bodies. And by this means upon the &s;ucce&s;&s;ive mo|tions of Bodies, there is maintained a &s;ucce&s;&s;ive and continual circulation in the motions, e&s;pecially of tho&s;e Bodies that are fluid, and &s;o more ready and apt for motion.</P>
<P>In the In&s;tance of my Pump, &s;uppo&s;e that the orifice at <HI>B</HI> be left open, and the ve&s;&s;el or Bottle have a Gallon of Water in it, and there &s;tands by it an empty ve&s;&s;el, &s;uppo&s;e <HI>M,</HI> that contains a Gal|lon of Air: if I pump out a Gallon of Water out of the Pump into the ve&s;&s;el <HI>M,</HI> as the Pump is gradually emptied of the Gallon of Water into <HI>M,</HI> the Water leaves its place in the Pump, and takes
<PB N="301" REF="154">up as much room in <HI>M,</HI> and the Air in <HI>M</HI> leaves as much &s;pace there, and takes it up in the Pump, to which it hath a free acce&s;s; &s;o that the two Ele|ments change their &s;tations, and while they hold their natural texture, hold the &s;ame exten&s;ion of &s;pace, though not the &s;ame &s;ituation. And thus a circulation is naturally con&s;equential upon the mo|tion e&s;epecially of fluid Bodies; and there|fore when the Water leaves its place in the Pump, and di&s;po&s;&s;e&s;&s;eth the Air in the ve&s;&s;el <HI>M,</HI> and the di&s;po&s;&s;e&s;&s;ed Air gradually &s;ucceeds into the &s;pace left by the Water, as fa&s;t as the Water leaves it, and takes up another room equal to what it had before, though in another <HI>ubi;</HI> here is no Gravitation of an At|mo&s;pherical column upon the orifice <HI>B,</HI> but only a natural motion and &s;ucce&s;&s;i|on of the like portion of Air into the place relicted by the Water, and a natu|ral de&s;ertion of that &s;pace which it be|fore had in the ve&s;&s;el <HI>M,</HI> which it can|not retain again&s;t the weightier and more prevalent Element of Water tak|ing it up. So that it is neither a Gravi|tation
<PB N="302" REF="155">of the atmo&s;pherical Cylinder upon the orifice <HI>B,</HI> nor any great Ela|&s;ticity of the Air that drives up the Wa|ter, but a natural circulation of the por|tion of Air into the &s;pace derelicted by the Water; and the immi&s;&s;ion or in&s;i|nuation of the Air into that Cavity, is the Effect not the Cau&s;e of the rece&s;&s;ion of the Water.</P>
<P>And now to reduce all this long pro|ce&s;s to the thing I principally intended, we are told by the late Philo&s;ophy, that the &s;u&s;pen&s;ion of the Mercury at twen|ty nine Inches height in the <HI>Torricellian</HI> Experiment, is cau&s;ed by the counter|poi&s;e of the weight of an external atmo|&s;pherical Column, commen&s;urate in its cra&s;&s;itude and weight to the Mercurial Cylinder &s;u&s;pended in the Gla&s;s Tube.</P>
<P>And when it is replied, that the like &s;u&s;pen&s;ion happens, if the Mercurial Engin be placed in a clo&s;e room, yea or in a Gla&s;s every way clo&s;ed, that admits not any &s;uch Mercurial column, but in|tercepts it and its pre&s;&s;ure by its clo&s;ure every way. We are again told, that that little portion of Air included with|in
<PB N="303" REF="155">that room or Gla&s;s, hath &s;o potent an Ela&s;ticity, that it will as effectually &s;u&s;pend the Mercury in the Tube, as that tall Atmo&s;pherical Cylinder of at lea&s;t &s;even Miles long. This I &s;ay &s;eems to me utterly incredible for the&s;e rea|&s;ons:</P>
<P N="1">1. The Air included in a clo&s;e room or Gla&s;s, hath only the advantage of its imagined Ela&s;ticity, but not the advan|tage of the &s;tupendous weight a&s;&s;igned by this New Philo&s;ophy to the external aereal Cylinder.</P>
<P>The external Air hath the &s;ame Ela|&s;ticity attributed to it, as the Air inclu|ded in the clo&s;e room or Gla&s;s, and al&s;o the &s;uppo&s;ed advantage of the weight of the Cylinder of the Atmo&s;phere be&s;ides.</P>
<P>If the bare Ela&s;ticity of inclo&s;ed Air be &s;ufficient to &s;u&s;pend the Mercury at twenty nine Inches and half, within the room or Gla&s;s; the &s;ame Ela&s;ticity in the external Air, with the advantage of its weight, &s;hould &s;u&s;pend the Mer|cury to fifty nine Inches high, which was never yet done.</P>
<P N="2">2. If the Elatery of the Air cannot
<PB N="304" REF="156">drive up a &s;ucce&s;&s;ive portion of Water of half an Inch diameter into my Pump, without the attraction of the <HI>Embolus;</HI> nor yet is that attraction al&s;o effectual to rai&s;e the Water, when it hath expanded the Air to about a fourth part of &s;pace more than is natural to it. It is impo&s;&s;i|ble that the Ela&s;ticity of the Air, inclu|ded in a clo&s;e room or Gla&s;s Receiver, can drive and keep up a Cylinder of Mercury twenty nine Inches high, which yet according to the amplitude of its diameter may weigh, two, four, or ten pound.</P>
<P>I do therefore conclude upon the whole matter, that it &s;eems to me, the new <HI>hypothe&s;is</HI> of the Weight and Ela&s;ti|city of the Air, as it is delivered by the late Philo&s;ophy, is an Ingenuous Inven|tion, but wants Reality to &s;upport it &s;elf, or to give a right and true Solution to the <HI>Phanomena</HI> wherereunto it is applyed.</P>
<TRAILER>FINIS.</TRAILER>
</DIV2>
</DIV1>
</BODY>
<BACK>
<DIV1 TYPE="table of contents">
<PB REF="156">
<HEAD>THE CONTENTS.</HEAD>
<LIST>
<ITEM><LABEL>CHAP. I.</LABEL> <HI>The Introduction, containing the order of the en&s;uing Enquiries.</HI> fol. I</ITEM>
<ITEM><LABEL>CHAP. II.</LABEL> <HI>The Explication of &s;ome Terms, that may be of u&s;e in the following Inquiry.</HI> II</ITEM>
<ITEM><LABEL>CHAP. III.</LABEL> <HI>Concerning the Gravitation of Bodies; and fir&s;t, concerning the Gravitation of Fluids, in relation to Fluids of the &s;ame kind and con&s;i&s;tence: And therein al&s;o, fir&s;t of the Gravitation of water upon Water.</HI> 30</ITEM>
<PB REF="157">
<ITEM><LABEL>CHAP. IV.</LABEL> <HI>Concerning the Gravitation of the Air upon Air, or any &s;ubjected Bodies in it.</HI> 47</ITEM>
<ITEM><LABEL>CHAP. V.</LABEL> <HI>Concerning the Gravitation of heavier Flu|ids upon tho&s;e that are lighter.</HI> 88</ITEM>
<ITEM><LABEL>CHAP. VI.</LABEL> <HI>Concerning the Pre&s;&s;ure or Gravitation of lighter Fluids, upon tho&s;e that are &s;pe|cifically heavier.</HI> 93</ITEM>
<ITEM><LABEL>CHAP. VII.</LABEL> <HI>Concerning the Space derelicted by the de|&s;cent of the Mercury in the</HI> Torricellian <HI>Experiment, and what it is not, or what it is that fills it.</HI> 117</ITEM>
<ITEM><LABEL>CHAP. VIII.</LABEL> <HI>Concerning the Body &s;upplying the derelicted
<PB REF="157">Space in the top of the Tube, and fir&s;t what it is not.</HI> 122</ITEM>
<ITEM><LABEL>CHAP. IX.</LABEL> <HI>Concerning the other Suppo&s;ition, namely, that this derelicted Space is filled with a Body</HI> ab intra. 131</ITEM>
<ITEM><LABEL>CHAP. X.</LABEL> <HI>The Enquiry touching the Cau&s;e that keeps the Mercury &s;u&s;pended in the Tube at twenty nine Inches, or thereabout; and fir&s;t what is not the Cau&s;e of this Su&s;pen|&s;ion.</HI> 147</ITEM>
<ITEM><LABEL>CHAP. XI.</LABEL> <HI>Concerning the &s;uppo&s;ition of the</HI> aequipon|dium <HI>of a pillar of the Air, or Atmo|&s;phere, as the Cau&s;e &s;u&s;taining the Mer|curial Cylinder.</HI> 152</ITEM>
<ITEM><LABEL>CHAP. XII.</LABEL> <HI>Touching the Elatery or Spring of the Air.</HI> 178</ITEM>
<PB REF="158">
<ITEM><LABEL>CHAP. XIII.</LABEL> <HI>Certain Experiments, evincing that the common Air in its ordinary con&s;i&s;tence, hath no, or no con&s;iderable Ela&s;ticity or Spring, without an accidental or preter|natural Compre&s;&s;ion.</HI> 195</ITEM>
<ITEM><LABEL>CHAP. XIV.</LABEL> <HI>The con&s;ideration of &s;ome Arguments for the weight and Elatery of the Air.</HI> 201</ITEM>
<ITEM><LABEL>CHAP. XV.</LABEL> <HI>Concerning the true Cau&s;e of the &s;u&s;pen&s;ion of the Mercury at twenty nine Inches and half, or thereabout, in the</HI> Torri|cellian <HI>Engin.</HI> 215</ITEM>
<ITEM><LABEL>CHAP. XVI.</LABEL> <HI>Concerning the two Suppo&s;itions that are nece&s;&s;ary to maintain this Solution,</HI> viz. <HI>Natures abhorrence of a</HI> vacuum, <HI>and the Attraction of ten&s;ible fluids, or o|ther
<PB REF="158">Bodies when under a ten&s;ion.</HI> 236</ITEM>
<ITEM><LABEL>CHAP. XVII.</LABEL> <HI>Concerning the Cau&s;e of the Cohe&s;ion of two poli&s;hed Marbles.</HI></ITEM>
<ITEM><LABEL>CHAP. XVIII.</LABEL> <HI>Concerning the</HI> Magdeburgh <HI>Hemi&s;pheres, and their cohe&s;ion, and the rea&s;on thereof.</HI> 262</ITEM>
<ITEM><LABEL>CHAP. XIX.</LABEL> <HI>Concerning the rai&s;ing of the water by Pumps or Syringes.</HI> 286</ITEM>
</LIST>
</DIV1>
<DIV1 TYPE="publisher's advertisement">
<PB REF="159">
<P><GAP DESC="illegible" EXTENT="1 word"> printed for, and to be &s;old by <HI>William Shrowsbury,</HI> at the &s;ign of the Bible <HI>in Duck-lane.</HI></P>
<P>AN E&s;&s;ay touching the <HI>Gravitation</HI> or <HI>Non-Gravitation</HI> of Fluid Bodies, and the rea|&s;ons thereof; in 8^o.</P>
<P><HI>Stereometrie,</HI> or the Art of <HI>Practical Gauging;</HI> &s;hewing in two Parts, 1. Diver&s;e facile and compendious ways for Gauging of <HI>Tuns</HI> and <HI>Brewers Ve&s;&s;els,</HI> of all Forms and Figures, ei|ther in whole, or gradually from Inch to Inch, whether the Tun or ve&s;&s;els Ba&s;es above and below be <HI>Homogeneal,</HI> or <HI>Heterogeneal,</HI> paral|lel and alike &s;ituate or not. 2. The Gauging of any <HI>Wine, Brandy,</HI> or <HI>Oyl-Cask;</HI> be the &s;ame a&s;&s;um'd as <HI>Sphaeroidael, Parabolicael, Co|nical,</HI> or <HI>Cylindrical;</HI> either full, or partly empty, and at any Po&s;ition of the <HI>Cask,</HI> or Al|titude of contained <HI>Liquor;</HI> performed either by brief <HI>Calculation,</HI> or <HI>In&s;trumental Opera|tion.</HI></P>
<P>Together with a Large <HI>Table</HI> of Area's of a Circles Segments, and other nece&s;&s;ary <HI>Tables,</HI> and their excellent Utilities and Improve|ments;
<PB REF="159">with a Copious and Methodical <HI>In|dex</HI> of the Whole; rendring the Work per|&s;picuous and intelligible to Mean Capacities. By <HI>John Smith,</HI> Philo-Accomptant: in 8^o.</P>
<P>Franconis Burger&s;dicii <HI>Idea Philo&s;ophiae Natura|lis, &s;ive Methodus definitionum &amp; controver&s;i|arum
Phy&s;icarum. Editio Novi&s;&s;ima.</HI></P>
<P><HI>Huc acce&s;&s;it Idea Oeconomicae &amp; Politicae Doctri|nae, codem Auctore. Opus Po&s;thumum.</HI> 12^o.</P>
<P><HI>De antiqua Eccle&s;iae Britannicae Libertate, atque de legitima eju&s;dem Eccle&s;iae exemptione &agrave; Ro|mano Patriarchatu Diatribe per aliquot The&s;es diducta: Autore</HI> I.B. SS. <HI>Theologiae Profe|&s;&s;ore.</HI> 4^o.</P>
</DIV1>
<DIV1 TYPE="illustrations">
<PB REF="160">
<P><FIGURE>
<FIGDESC>schematic diagrams</FIGDESC>
</FIGURE></P>
<PB REF="161">
<P><FIGURE>
<FIGDESC>schematic diagrams</FIGDESC>
</FIGURE></P>
</DIV1>
</BACK>
</TEXT>
</EEBO>
</ETS>
