1887.] Lt.-Col. Waterhouse exhibited photographs. 97 



I may also mention that these plates have been found very valuable 

 in photomicrographical researches for photographing stained preparations, 

 and will be useful for many other purposes where a better represen- 

 tation of the so-called non-actinic colours is required than can be ob- 

 tained on ordinary plates. 



Lieut.-Colonel Waterhouse exhibited some specimens of heliogravure 

 lately produced in the Survey of India offices and made the following 

 remarks :—* 



The two plates of archaeological subjects and a quarter sheet of the 

 Atlas of India, I have brought to show you this evening, have all been 

 reproduced by the photo-electrotype process from manuscript drawings. 

 The two first are from the beautiful collection of drawings of Archaeo- 

 logical Remains in the Bombay Presidency executed under the super- 

 intendence of Dr. Burgess and were especially selected by Sir E. Buck 

 to test the capabilities of the process. The map was drawn in the 

 Survey of India office with particular care that it might reproduce the 

 effect of an engraved Atlas sheet when slightly reduced. 



The way of obtaining these plates has already been described in the 

 Society's Journal, Part II, No. 2. 1878, p. 100, but we now use an 

 improved gelatine tissue, specially manufactured by the Autotype Com- 

 pany, containing plumbago and other substances which give a certain 

 roughness or ' grain ' to the gelatine image and at the same time render it 

 conductive of electricity so that when the print has been developed on 

 the silvered copper plate and dried it is ready to go into the electro- 

 typing battery. 



We have also improved the electrotyping arrangements, and now 

 use a form of battery I first saw in use at Vienna, consisting of two 

 troughs ; an outer one, containing solution of sulphate of copper, and an 

 inner one having a leather bottom and containing dilute sulphuric acid. 

 An iron plate is placed in the inner trough and coupled to the silvered cop- 

 per plate bearing the gelatine matrix, placed below it on a suitable support 

 in the lower trough. Electrical action is set up so that copper is deposited 

 on the matrix and in the course of 3 to 4 weeks a plate is produced of suffi- 

 cient thickness to stand printing from. The deposited plate is then 

 separated from the matrix and after a little cleaning is ready for printing 

 in the copper plate press. 



The process is not an expensive one and is exceedingly cheap when 

 compared with hand-engraving, A plate of most close and elaborate 

 design that would take months or even a year or two to engrave by hand 

 can in this way be reproduced in a month or six weeks. In the case of 



