82 JOUtiNAL AND PROCEEDINGS 



his negatives, using albumen and starch mixed with iodine, sensi- 

 tized with silver and developed and fixed with potassium bromide. 

 This in 1847. Then comes the great stream of progress. Blau- 

 quart Evraud introduced albumen on paper, still in use greatly 

 perfected. 



Next in the great march of photographic progress, lyC Gray of 

 Paris employs in place of albumen on glass a solution of gun cotton 

 in alcohol and ether. His method was given practical shape by 

 Scott Archer, henceforth known as the wet collodion process — 

 practicall}' the wet collodion process of to-day. 



The great uncertaint}^ of the silver bath in this former process 

 soon led to further modifications. Sayce and W. B. Bolton in 1864 

 produced the collodion emulsion process, which has lasted until 

 now. First came the washing of the soluble nitrates from the 

 emulsion after coating ; then washing of the emulsion in bulk, and 

 more recently the color sensitizing of the emulsion. 



First a word on Archer's process, practically a "dry plate 

 bath " process, according to the prescriptions of Taupenot, and 

 others, about 1855, and from that date many other " preservatives " 

 (pyrogallic acid, sugar, beer, etc.) were used. 



The next advance is linked with collodion emulsion. In 1871, 

 Dr. Maddox substituted aqueous gelatine solution for the spiritu- 

 ous collodion and found the same a possible photographic prepara- 

 tion. This '' gelatino-bromide process" — so momentous in the 

 history of photography — was worked out by Burgess, Kennett and 

 Wratten, to name only three of the investigators, and Kennett, 

 about 1874-1877, put gelatine plates upon the market. Of the fur- 

 ther history of gelatine emulsion little need be said. 



We have thus traversed three quarters of a century in our brief 

 review of photographic progress, in which have been noted in gen- 

 eral the physical and chemical developments of so man}' of the 

 pioneers of this useful art, from which so many of us derive so 

 much pleasure, and which is immeasurable in its widespread bene- 

 fits. We include the several concurrent methods of the preparation 

 of the dry plate akin to its present adaptability ; to the preparation 



