492 ANNUAL RECORD OF SCIENCE AND INDUSTRY. 



This sensitiveness, however, was much affected by the method 

 of development. In attempting to prepare bromide of silver 

 plates with his own hands, he found no repetition of the phe- 

 nomenon which he had noticed on the English plates ; and, 

 reasoning upon the subject, he conjectured that the English 

 plates must contain some substance that absorbs the green 

 rays in a greater measure than the blue. Noticing that the 

 English plates had, among other things, a yellow coloring mat- 

 ter as a coating, he made an attempt to impregnate bromide 

 of silver with a substance that should absorb especially the 

 yellow rays. The substance he chose was coralline dissolved 

 in alcohol. The plates prepared in this way were of a de- 

 cided red tint, and on exposure to the spectrum they proved 

 specially sensitive in the indigo and in the yellow, and of 

 diminished sensitiveness in the intermediate portions of the 

 spectrum. Thus a method was attained of preparing bro- 

 mide of silver plates that were acted upon almost as strongly 

 by a color hitherto held to be chemically inert namely, yel- 

 low as they were by the indigo blue. Proceeding further in 

 his experiments, he found among the green aniline products 

 a body endowed with a powerful absorption of red rays, by 

 means of which he heightened the sensitiveness of his bro- 

 mide plate to that color. From these results he thinks he is 

 Avell justified in inferring that we are in a position to render 

 bromide of silver sensitive to any color that we may choose. 

 These experiments, both in a practical and theoretical point 

 of view, cover a somewhat different field from those of Dr. 

 Draper, of New York, who thirty years ago demonstrated 

 that any color whatever could be photographed by employ- 

 ing a properly selected chemical for preparing the sensitive 

 plate. 



MECHANICAL PHOTOGRAPHIC PRINTING WITHOUT A PRESS. 



The following process, devised by Jacobsen, requires no 

 press, and is adapted to printing on round objects, as vases, 

 bottles, etc., and indeed may, perhaps, be used with colors 

 that are to be burned in. A carbon picture, formed in the 

 usual way on a glass plate, is surrounded by a wooden frame 

 which fits closely to the glass, and into which is poured, 

 when not too warm, a mixture of one part of gelatine, one 

 part of gum arabic, and two parts of glycerine. When this 



