PRACTICAL PHOTOMICROGRAPHY. 153 



from the hydroquinone, the two solutions will keep for a long 

 time, and may be mixed at time of need. 



This developer acts very steadily ; if exposure has been 

 sufficient failure can hardly occur with suitable negatives and 

 good plates, for the developing action only requires to be 

 watched and stopped at the proper time. Fixing, washing, 

 and clearing may be conducted as usual. This developer is 

 strongly recommended for Bromide prints. 



ALKALINE PYRO DEVELOPER. 



This is not recommended for our purpose unless there be 

 some special desire for warm tones. Sodic Sulphite as a pyro 

 preservative is to be avoided and preference given to potassic 

 meta-bisulphite see page 61. An ounce of developer may 

 be made to contain : 



Pyro 1 to 1J^ grain. 



Potassic Meta-bisulphite 2 to 3 grains. 



Liquor Ammonia. 880 . . .2 minims. 



Potassic or Ammonic Bromide. . . . 2 grains. 



Water to 1 ounce. 



The rationale of developers, of which the above may be 

 called illustrative, is simply a well restrained development, the 

 potassic salt tending to produce a warm tone, coupled with full 

 exposure and " willing " development. 



Here again fixing and washing are as usual, except that after 

 fixation if a warm tone be desired and not previously obtained, 

 the washing should be little more than a rinse, and the acid- 

 iron-alum solution applied as before will greatly redden the 

 color of the image while clearing the high lights. 



All lantern slides should be varnished with a clear varnish, 

 usually certain colorless gums dissolved in benzole. 



To mount a lantern slide. Clean a thin, flawless glass plate 

 3J inches square ; select and lay in position upon the face of 

 the slide a suitable mask ; on the mask lay the cleaned cover- 

 glass. Wet a gummed " strip," which ought to be about fths 

 of an inch wide and 14 inches long ; lay one side of the now- 

 protected slide in the middle and at one end of the wetted 

 strip ; turn the slide over side by side, always lifting with it 



