LOUIS JACQUES MANDE DAGUERRE (1789-1851), a French painter aud physicist, was born at Cormeilles, in the department of Seine-et-Oise, and died July 12, 1851, at Petit-Brie-sur-Marne, near Paris. He was at first occupied as an inland revenue officer, but soon betook himself to scene-painting for the opera, in which he ere long surpassed his predecessors Bibieua and Munich, and his teacher Degoti, more especially in his remarkable power of representing light and shade. Among the most admired of his productions were the Chapel of Glenthorn, at the Ambigu, and the Rising of the Sun in " Les Mexicains." He assisted M. Prévost in the execution of panoramic views of Rome, Naples, London, Jerusalem, and Athens, and subsequently (July 11, 1822), in conjunction with Bouton, he opened at Paris the Diorama (Sis, double ; opafna, view), an exhibition of pictorial views, the effect of which was heightened by changes in the light thrown upon them. As an example of these may be instanced the Midnight Mass at the Church of Saint-Étienne du Mont. An establishment similar to that at Paris was opened by Daguerre in the Regent's Park, London. On the 3d March 1839 the Diorama, together with the work on which Daguerre was then engaged, the Interior of Sainte-Marie-Majeure, was destroyed by fire. This reverse of fortune was soon, however, more than compensated for by the distinction he achieved as the inventor of the daguerreotype photographic process. Nicéphore Niepce, who since 1814 had been seeking a means of obtaining permanent pictures by the action of sunlight, learned in 1826 that Daguerre was similarly occupied. In the following year he communicated to Daguerre particulars of his method of fixing the images produced in the camera lucida by making use of metallic plates coated with a composition of asphalt and oil of lavender ; this where acted on by the light remained undissolved when the plate was plunged into a mixture of petroleum and oil of lavender, and the development of the image was effected by the action of acids and other chemical reagents on the exposed surface of the plate. The two investigators laboured together in the production of their " heliogiaphic pictures " from 1829 until the death of Niepce, July 3, 1833. Daguerre, continuing his experiments, discovered eventually the process connected with his name. This, as he described it, consists of five operations :—the polishing of the silver plate; the coating of the plate with iodide of silver by submitting it for about 20 minutes to the action of iodine vapour ; the projection of the image of the object upon the golden-coloured iodized surface ; the development of the latent image by means of the vapour of mercury ; and, lastly, the fixing of the picture by immersing the plate in a solution of sodium " hyposulphite" (sodium thiosulphate). On January 9, 1839, at a meeting of the Academy of Sciences, Arago dwelt on the importance of the discovery of the daguerreotype ; and, in consequence of the representations made by him and Gay Lussac to the French Government, Daguerre was on the 15th of June appointed an officer of the Legion of Honour. On the same day a bill wa3 presented to the Chambers, according to the provisions of which Daguerre and the heir of Niepce were to receive annuities of 6000 and 4000 francs respectively, on the condition that their process should be made known to the Academy. The bill having been approved at the meetings of the two Chambers on the 9th of July and the 2d of August, Daguerre's process, together with his system of transparent and opaque painting, was published by the Government, and soon became generally known. The first great improvement upon it, due to Mr Towson of Devonport, was the use of enlarged lenses, with which Mr Draper of New York was the first to secure portraits from the life. Then followed Mr Goddard's introduction, in 1840, of bromine for increasing the sensitiveness of the plates, and Fizeau's method of strengthening the lights and shades by the application of chloride of gold in the fixing operation. Previous to the time of Daguerre both Wedgwood and Sir H. Davy had attempted, but in vain, to prevent the unshaded portions of pictures taken by means of the solar rays from becoming coloured by exposure to diffused light ; this result Daguerre secured by the use of sodium thiosulphate, and thus became the chief pioneer of the modern art of photography.

Daguerre's Historique et description des procédés du Daguerréotype et du Diorama (Paris, 1839), passed through, several editions, and was translated into English. Besides this he wrote an octavo work, entitled Nouveau moyen de préparer la couche sensible des plaques destinées à recevoir les images photographiques (Paris, 1844).