200 SEC. 7. LIGHT. 



924. A selection of eight fluorescent liquids. 



Dr. Th. Schuchardt, Gbrlitz. 



VII. PHOTOGRAPHY. 

 a. PHOTOGRAPHIC PROCESSES. 



925. Frame containing glass negative, gelatine "relief," 

 leaden " mould," and impression from the latter, showing the 

 various stages in the production of a "Woodbury" permanent 

 photograph. 



Woodbury Permanent Photographic Printing Company. 



926. Frame containing transparencies for the magic lantern, 

 printed by the " Woodbury " process. 



Woodbury Permanent Photographic Printing Company. 



927. Specimens of Willis's Aniline Process. Printed 

 from tracings by Vincent Brooks, Day and Son. 



William Willis, Bromley -, Kent. 



This is a method of photographic printing differing greatly from all other 

 kinds in the chemical actions involved and in the manipulations required. The 

 blacks of the picture are produced by the action of aniline vapour on free 

 chromic acid ; the paper having been first coated with the latter substance, 

 and exposed to light under the drawing to be copied. On placing this 

 exposed sheet in a chamber filled with aniline vapour the yellow unaltered 

 chromic acid becomes speedily blackened, and produces a permanent print. 

 No negative is required, but a positive print is obtained by one operation 

 from a positive original. The principal application of the process is the 

 copying of engineers' and architects' tracings. 



928. Willis's Platinum Printing Process. 



Wm. Willis, fun., Birmingham. 



This is a method of photographic printing by which the picture is made to 

 consist of platinum black instead of silver. The reduction of the platinum 

 salt, with which the paper is coated, is effected by the action of light on a 

 persalt of iron, which forms an additional coating to the paper, followed by 

 a floating of the print on a solution of potassic oxalate. 



928a. Illustrations of the Heliotype Process. 



J. B. Edwards and Co. 



The photographs are printed in printers' ink, at an ordinary printing press, 

 from a film of gelatine, whereon the photographic image has been imprinted 

 by the action of light. 



1 . A gelatine film ready for exposure to light under the negative. 



2. A film laid down upon a metal plate and inked up ready for printing 

 from. 



3. A proof in permanent ink from the same film. 



