192 HISTORY OF PHOTOGRAPHY. 



In a short time the glass will be covered with a very beautiful metallic 

 coating. The solution is now poured off, the edging of wax removed, 

 and the silver is exposed to the action of diluted chlorine, or to the 

 vapor of iodine or bromide, until it is converted into a compound 

 of one of these elements, after which we may proceed as recommended 

 by Sir John Herschel. 



ALBUMEN. 



In the Technologiste for 1848, M. Xiepce de Saint-Victor published 

 his mode of applying albumen to glass plates. M. Blanquart Ever- 

 ard followed, and successively albumen, gelatine, and serum were 

 employed. Messrs. Ross and Thomson, of Edinburgh, have been 

 eminently successful operators with albumen on glass plates, many 

 of their pictures leaving little to be desired. The manipulatory 

 details of the albumen process will be found in the technical division 

 of this work. 



COLLODION. 



The successful application of a solution of gun cotton in ether, 

 to form the film for receiving the sensitive surface on glass, has been 

 claimed respectively by Mr. P^ry and Mr. Archer. There is some 

 difficulty in fixing precisely this point, since there was no actual 

 publication of the process imtil long after it was generally in use. 

 Mr. P'l-y certainly introduced the use of gutta-percha in combination 

 with collodion. 



