100 J. WaterhousC' — The Application of ^Jiotograpliy No. 2, 



The leaden plate or mould is laid in a suitable press of peculiar con- 

 struction* and slightly greased. A small quantity of the coloured gelatine 

 having been poured in a liquid state into the middle of the mould, a piece of 

 suitable paper is laid above it and pressed strongly down, so as to force the 

 ink thoroughly into the depressions all over the plate and squeeze out all the 

 ink between the surface of the metal and the paper in the parts forming 

 the highest lights of the picture. The gelatinous ink is allowed a short 

 time to * set' and attach itself to the paper ; the paper is then removed and 

 brings with it a perfect impression of the j^icture in coloured gelatine, of 

 different thicknesses corresponding in intensity and gradation of shade to the 

 depth in different parts of the plate. The print has now only to be 

 ' fixed' in a solution of alum and when dry is perfectly permanent and 

 ready to be trimmed and mounted. 



The rate of imj)ression is about the same as of ordinary copper-plate 

 printing and may be carried on quite indej^endently of the light. If very 

 large numbers are required of a single subject, it is easy to produce as many 

 printing plates as may be required from the original gelatine relief, which 

 may afterwards be put away and kept indefinitely. The cost of printing 

 is exceedingly small and prints are jDroduced in large numbers at a marvel- 

 lously cheap rate. As the process requires special mechanical apj^liances 

 and apparatus it has generally been worked on the large scale by public 

 companies. 



The Woodbury-type is unfortunately not well adapted for the repro- 

 duction of maps, because it has been found very difficult to produce im- 

 pressions of large dimensions, and, owing to the peculiar method of printing, 

 it is almost impossible to obtain the clear black lines and pure white ground 

 so indispensable in a good map. The prints also have to be mounted, 

 which is an objection. However, in special cases where the work is within 

 the cajmbilities of the process, it will be found valuable, because it possesses 

 the great advantage over the collotype processes for the reproduction of 

 half-tone subjects that the printing of an almost indefinite number of 

 copies can be carried on with as perfect certainty as in ordinary litho- 

 graphy or engraving, while in beauty, transparency and delicacy of grada- 

 tion the Woodbury-type prints are undoubtedly superior to collotypes. 



VIII. PnoTOGEAPHic Engeatinq. 



As was noticed in the Introduction, the earliest practical process of 

 photography was a methoil of photographic engraving invented by Nice- 

 phore Niepce, and since his time nearly every great improvement in photo- 

 graphy has been applied to this object. Thus, no sooner was the Daguerre- 

 otype invented than essays were made by Fizeau, Donne and others to engrave 



* For a drawing of this press, see Abney's Treatise on Photograjjhy, p. 175. 



