148 



THE PRODUCTION OF POSITIVES, ETC. 



After focussing, the smallest stop compatible with 

 a proper differentiation of the several shades in the 

 negative should be inserted, and an exposure accord- 

 ing to the size of the enlargement and density of the 

 negative being given, the usual manipulations are 

 proceeded with. 



The advantage this method possesses over that to 

 be described, is the possibility of enlarging from a 

 negative of any size. This, however, can be accom- 

 plished by other means, and is only mentioned as an 

 additional resource where time is important, or 

 where the markings are so fine that they would be 

 injured by the coarseness of the film on dry plates, 

 when the collodion process is not available for the 

 production of a reduced negative. 



An ordinary magic lantern, the condensers of 

 which are not less than four and a half inches in 

 diameter, answers excellently when placed in the 

 recess of the dark room. The entrance of actinic 

 light being prevented by fastening the sleeve in- 

 tended for the microscope over the nozzle of the 

 lantern. 



The focus is obtained by pinning a sheet of white 

 paper on a moveable stand, and substituting the sen- 

 sitized surface for it after placing a cap over the 

 nozzle. The latter operation is much facilitated, if a 

 piece of ruby glass is let into the cap. 



Many artists prefer the delicate tone of the ordin- 

 ary silver print to that produced on a gelatino-bro- 

 mide surface. All that is then necessary is the 

 production of a positive on paper, if a negative by 



