-- 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.
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 Institution.
-- "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 potassium 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.