A Manual Of Photography

26 HISTORY OF PHOTOGRAPHY. clear in their details to be readily recognised, and which, more- over, being obtained with rapidity, by an easy manipulation, may be kept with very little care, comprised in great number in a small compass, and moved from place to place with facility. Mr. Talbot s papers already present many of these essential qualities, with the advantage of being able to furnish numerous copies immediately. His efforts, and those of others occupied with the same subject, will conclude by adding to them everything which may be desirable, provided that expectation, or the pretension ot a perfection of art physically incompatible with operations on paper, do not give a false direction to their endeavours. How- ever, not to appear to despair too much of the future, I may add that the height of success would consist in discovering a sub- stance very susceptible of receiving impressions, which might be applied on a papyraceous leaf without penetrating deep into it, and which might, however, be fixed in it after the operation, as in Mr. Talbot's impressions. It does not seem necessary even that the first impression thus rapidly obtained should copy the lights and shades in their proper places, provided that its trans- parency and fixedness were such, that we might deduce them from the application of copies wherein the inversion would be corrected. And perhaps, by this decomposition of the problem into two successive operations, one of the best ways is opened by which it may be resolved.” Numerous improvementshave beenintroduced,butstillphysical difficulties, such as those which he has indicated, surround the photographic processes, and even where M. Biot has proved wrong in his conjectures, bis remarks form a curious chapter in the history of the art. Mr. Talbot’s description of his process, the patent for which is dated 1841, is as follows1 :— Take a sheet of the best writing-paper, having a smooth sur- face, and a close and even texture. The water-mark, if any, should be cut off, lest it should injure the appearance of the picture. Dissolve 100 grains of crystallised nitrate of silver in six ounces of distilled water. Wash the paper with this solution with a soft brush on one side, and put a mark on that side, whereby to know it again. Dry the paper cautiously at a dis- tance from the fire, or else let it dry spontaneously in a dark room. When dry, or nearly so, dip it into a solution of iodide of potassium, containing 500 grains of that salt dissolved in one pint of water, and let it stay two or three minutes in the solu- tion. Then dip the paper into a vessel of water, dry it lightly 1 August 13, 1852.—Mr. Talbot has, by a letter in the Times of to-day, given his patents to the publie. The letter is printed in the Appendix.