102 ELEMENTARY PHOTO-MICROGRAPHY. 



For high powers (rapid), Imperial " Sovereign." 



For colour contrasts, Ilford "Versatile Ortho.," 

 Imperial "N.F." (non-filter), and "Wratten" 

 plates. 



For lantern slides, Ilford " Special " and Cadett 

 Black Tone. 



Backed plates give better negatives, but 

 are messy, so, until the worker gains experience, 

 it is better for him to commence with the un- 

 backed plates. For negatives of any kind nothing 

 beats the pyro-soda developer. 



It is believed that backed plates require longer 

 exposure than plates not backed, though if any 

 difference in speed it is quite imperceptible, and 

 some makers of well-known brands state that 

 " backing " makes no difference whatever. Backed 

 plates, however, ought not to be kept in stock quite 

 so long as plates not backed. 



PYRO-SODA DEVELOPER. 



No. i, or A. 



Pyrogallic acid . . . . 60 grains. 

 Potassium metabisulphite . . 15 

 Water . . . . . . 10 ounces. 



No. 2, or B. 



Washing soda . . . . I ounce. 



Sodium sulphite . . . . i 



Water 10 ounces. 



