80 PHOTOGRAPHIC PROCESSES. 



double dry form, two sheets of zinc the same size as 

 the plate, each covered with black velvet on one side 

 and having a spring between them, should bo placed 

 with the velvet side next the back of the plates, in 

 the dark slide. 



These plates can now be purchased so cheaply, 

 with the degree of sensitiveness as regards collodion 

 marked on each box, that we do not recommend the 

 amateur to attempt their manufacture. As a prac- 

 tical knowledge of their preparation may be an as- 

 sistance, a description is appended of a process 

 which has afforded excellent results. 



The preparation of the following solutions may be 

 carried out in daylight. 



No I. Bromide of Potassium, 43 grs. 

 Nelson's Gelatine, 10 grs. 

 Distilled Water, 6 drachms. 

 One p. e. solution of hydrochloric acid, 

 10 minims. 



This solution, is put aside, and we place in another 

 earthenware vessel — 



No. II. 60 grains of special hard dry plate 

 gelatine, covering it with three or 

 four ounces of water. 



Both are allowed to soak for twenty-four hours. 

 All the following manipulations are done in non- 

 actinic light. 



No. III. Nitrate of Silver pure, 50 grs. 

 Distilled Water, 1 ounce. 



