ELEMENTARY PHOTO-MICROGRAPHY. 75 



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



For colour contrasts, Chromatic (Ilford). 



For lantern slides, Ilford " Special " and 

 " Alpha," and Cadett Black tone. 



The " Special " Ilford plate gives warm and 

 cold tones of black, and the " Alpha " gives 

 browns and reds. 



It is well to use both and have a variety of 

 colours. 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. 



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. 



Four drams of A and four drams of B, with five 



drops of 10% solution of potassium bromide, are 



taken for a quarter-plate. 



For lantern slides the writer finds that hydro- 



kinone is the most generally convenient. It may 



be made up as follows : 



