502 ANNUAL RECORD OF SCIENCE AND INDUSTRY. 



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pregnation with a bichromate solution, and exposed to light 

 under a negative. Subsequent immersion in warm water re- 

 moves the soluble portion from the surface, and leaves a thin 

 gelatine plate, upon which the image is represented in relief. 

 This matrix is then hardened with alum, and placed, when 

 dry, in a hydraulic press in contact with a plate of type-metal. 

 Under extreme pressure, applied gradually, the type-metal 

 takes the impression of the relief, and thus becomes actually 

 an engraved plate, in which the darkest shadows are repre- 

 sented by the deepest hollows, the half-tones by slight undu- 

 lations, while in the high lights there is no depression at all. 

 For the purpose of printing copies, a little pool of gelatine 

 ink is poured upon a sheet of white paper, and the metal 

 plate is brought down upon the same with some pressure, all 

 superfluous ink is at once pressed out, and after a few seconds 

 (to allow the warm ink to cool) the plate is raised, and a 

 beautifully shaded print is seen, in which the shadows and 

 half-tones are formed by layers of ink of different thicknesses. 

 As the matrix can be used in the preparation of several dozen 

 of plates, all of which can be printed simultaneously by hav- 

 ing a' suitable number of operators, many .copies of a given 

 print can .be printed daily without involving the use of light 

 in any way. The reprints are so perfect and delicate as to be 

 actually mistaken sometimes for silver prints, and are, at the 

 same time, absolutely permanent. This method is, perhaps, 

 better adapted to the reproduction of photograj^hic prints in 

 large editions than any other that has been devised, and can 

 be applied with equal advantage to all branches of illustra- 

 tion. An establishment for carrying on the Woodbury pro- 

 cess has lately been started in Philadelphia, under the direc- 

 tion of Mr. Garbutt, of Chicago, who, it is understood, has 

 purchased the right- to use this patent in the United States. 

 The principal objection made to this method is that the prints 

 require to be trimmed and mounted, instead of being made 

 directly upon the plate-paper like a lithograph. The Albert 

 process is also being w T orked in New York under the original 

 patent. The Philadelphia Photographic 'World for January 

 last contains a portrait of Mr. George W. Childs, printed by 

 the Woodbury process, of which five thousand impressions 

 were made from a single negative in twenty days. 12 A, 

 January 5, 1871, 18*7. 



