10 Waterhouse — Electrical action of Light upon Silver. [No. 1, 



Some Observations of the Electrical action of Light upon Silver and its 

 Haloid Compounds : — By Colonel J. Waterhouse, I. S. C, Assistant 

 Surveyor General of India. 



[Received April 20th : Read May 3rd.] 



In my paper on " Electro-chemical Reversals with Thio-carbamides,' ' 

 read at the meeting of the Society in April 1891, it was shown that 

 the peculiar reversals of the photographic image produced by the 

 addition of very minute quantities of a thio-carbamide, or sulpho- 

 urea, to an eikonogen developer appeared to be connected with and 

 accompanied by electro-chemical action, if not actually brought about 

 by it. It was remarked also that the experiments brought forward 

 pointed to the conclusion that, at any rate as regards the haloid salts 

 of silver, the formation and development of the photographic image 

 is to a very great extent influenced by electrical action, more so per- 

 haps, than has generally been recognised, although the fact of pho- 

 tographic action being accompanied by electrical phenomena has been 

 known since the earliest days of photography. It was suggested that 

 a further investigation into the theory of photography based on electro- 

 chemical laws, might be of value in throwing light upon much that 

 is now obscure and uncertain as regards the formation and development 

 of the invisible photographic image formed by the exposure to light 

 of silver haloid compounds. 



Since that time I have given a good deal of attention to the 

 subject and tried several experiments in various ways with the object 

 of ascertaining the electrical action of light, in connection with photo- 

 graphy, on plates of pure silver immersed in various fluids as well as 

 on dry plates and other forms of silver haloid compounds in ordinary 

 photographic use. Also on the action of electrical currents in forming 

 developable compounds of silver haloids similar to those formed by 

 light, and, further, on the electrolysis of ordinary photographic develo- 

 pers and on the cuivrents produced during the development of the 

 photographic image. These observations are not yet sufficiently com- 

 plete to found any sound deductions upon, but I hope to complete 

 them later. In the meantime, I have thought that a short note on 

 some observations I have lately made on the electrical action of 

 light upon plain silver plates in various solutions, might be of interest 

 and form a suitable introduction to any further notes on this subject I 

 may be able to bring before you. It does not pretend to be complete 

 or exhaustive, and can only be considered as a contribution towards a 

 systematic investigation of the question. 



