1829. Niepce 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 Inst.i.tution, 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 G.o.ddard, of London, inventor of the polariscope and lecturer on chemistry, employed chlorine added to iodine, and afterwards bromine, as accelerators in the Daguerreotype process.

1840. Antoine F. J. Claudet, F.R.S., of London, employed chlorine for the same purpose.

-- M. Fizeau, of Paris, deposited a film of gold over the Daguerreotype picture after the removal of the iodine, which imparted increased brilliancy and permanency.

-- Chloride of platinum employed by Herschel.

-- Fox Talbot's developer published September 20th.

1841. Calotype process patented by Fox Talbot, September 20th.

-- First photographic compound portrait lens made by Andrew Ross, London.

-- Towson, of Liverpool, noted that chemical and visual foci did not coincide. Defect corrected by J. Petzval, of Vienna, for Voightlander.

-- "A Popular Treatise on the Art of Photography, including Daguerreotype and all the New Methods of Producing Pictures by the Chemical Agency of Light," by Robert Hunt, published by R. Griffin, Glasgow.

-- Daguerre announced an instantaneous process, but it was not successful.

1842. Sir John Herschel exhibited blue, red, and purple photographs at the Royal Inst.i.tution.

-- "Photography Familiarly Explained," by W. R. Baxter, London.

1843. "Photogenic Manipulation," by G. T. Fisher Knight, Foster Lane.

-- Treatise on Photography by N. P. Lerebours, translated by J. Egerton.

1844. Fox Talbot issued "The Pencil of Nature," a book of silver prints from calotype negatives.

-- C. Cundell, of London, employed and published the use of bromide of pota.s.sium in the calotype process.

1844. "Researches on Light and its Chemical Relations," by Robert Hunt.

First edition; second ditto, 1854.

-- Robert Hunt recommended proto-sulphate of iron as a developer for Talbot's calotype negatives; also oxalate of iron and acetate of lead for other purposes.

-- A. F. J. Claudet patented a red light for "dark room," but at that date a red light was not necessary, so the old photographers continued the use of yellow lights.

1845. "Photogenic Manipulations:" Part 1, Calotype, &c.; Part 2, Daguerreotype. By George Thomas Fisher, jun. Published by George Knight and Sons, London.

-- "Manual of Photography," including Daguerreotype, Calotype, &c., by Jabez Hogg. First edition. Second ditto, including Archer's collodion process, bichloride of mercury bleaching and intensifying, and gutta-percha transfer process, 1856.

1845. "Practical Hints on the Daguerreotype; Willats's Scientific Manuals."

-- "Plain Directions for Obtaining Photographic Pictures by the Calotype and other processes, on paper; Willats's Scientific Manuals." Published by Willats, 98, Cheapside; and Sherwood, Gilbert, and Piper, Paternoster Row.

1846. Gun-cotton made known by Professor Schonbein, of Basel.

1847. Collodion made by dissolving gun-cotton in ether and alcohol, by Mr. Maynard, of Boston, U.S.

1848. "Photogenic Manipulation:" Part II., Daguerreotype, by Robert Bingham. Published by George Knight and Sons, London.

-- Alb.u.men on gla.s.s plates first employed for making negatives by M.

Niepce de Saint Victor. Process published June 13th.

-- Frederick Scott Archer experimented with paper pulp, tanno-gelatine, and iodised collodion, and made collodion negatives in the autumn.

1849. Collodion _positive_ of Hever Castle, Kent, made by Frederick Scott Archer _early_ in the year.

-- M. Gustave Le Gray _suggested_ the application of collodion to photography.