-- Iodide of silver made by Sir H. Davy. 1819. Sir John Herschel published the fact that hyposulphite of soda dissolved chloride and other salts of silver. 1824. Niépce obtained pictures in the camera-obscura upon metal plates coated with asphaltum, or bitumen of Judea. -- L. G. M. Daguerre commenced his researches. -- Permanganate of potash. Fromenkerz. 1826. Bromine discovered in sea-water by M. Balard. -- Bromine of silver made. 1827. Niépce exhibited his pictures in England, and left one or more, now in the British Museum. 1829. Niépce and Daguerre entered into an alliance to pursue their researches mutually. 1832. Evidence of Daguerre employing iodine. 1837. Rev. J. B. Reade, of Clapham, London, obtained a photograph in the solar microscope, and employed tannin as an accelerator and hyposulphite of soda as a fixer for the first time in photography. 1838. Reflecting stereoscope exhibited by Charles Wheatstone. -- Mungo Ponton observed that light altered and hardened bichromate of potash, and produced yellow photographs with that material. This discovery led to the invention of the Autotype, Woodburytype, Collotype, and other methods of photo-mechanical printing. 1839. Daguerre's success communicated to the Academy of Science, Paris, by M. Arago, January 7th. -- Electrotype process announced. -- Professor Faraday described Fox Talbot's new method of photogenic drawing to the members of the Royal Institution, January 25th. -- Fox Talbot read a paper, giving a full description of his process, before the Royal Society, January 31st. -- Sir John Herschel introduced hyposulphite of soda as a fixing agent, February 14th. -- Dr. Alfred Swaine Taylor employed ammonia nitrate of silver in preference to chloride of silver for making photogenic drawings, and employed hyposulphite of lime in preference to hyposulphite of soda for fixing. -- Daguerre's process published in August, and patent, for England, granted to Mr. Beard, London, August 14th. -- "History and Practice of Photogenic Drawing"; L. S. M. Daguerre. Published September. -- First photographic portrait taken on a Daguerreotype plate by Professor. J. W. Draper, New York, U.S., in the autumn of this year. 1840. "On the Art of Photogenic Drawing," by Alfred S. Taylor, lecturer on chemistry, &c., at Guy's Hospital. Published by Jeffrey, George Yard, Lombard Street, London. -- "The Handbook of Heliography, or the Art of Writing or Drawing by the Effect of Sunlight, with the Art of Dioramic Painting, as practised by M. Daguerre." Anon. -- Wolcott's reflecting camera brought from America to England and secured by Mr. Beard, patentee of the Daguerreotype process. -- The moon photographed for the first time by Dr. J. W. Draper, of New York, on a Daguerreotype plate. -- John Frederick Goddard, of London, inventor of the polariscope and lecturer on chemistry, employed chlorine added to iodine, and afterwards bromine, as accelerators in the Daguerreotype process.