120 ELEMENTARY PHOTO-MICROGRAPHY. 



that printing is not carried too far. As develop- 

 ment is very rapid, the exposure must be correct 

 to get good results. After a few trials it will not 

 be found at all difficult to determine when to stop 

 printing. The developing bath, which should not 

 be below 60 F., is made up of 



Neutral potassium oxalate . . i ounce. 



Oxalic acid (saturated solution) 



i part to 20 parts of developer. 



Water 10 ounces. 



This is a stock solution, and may be bottled for 

 future use. The paper is floated on the bath, face 

 downwards, turned quickly over, and development 

 watched. A black and white image will rapidly 

 appear, and when sufficient depth of tone is 

 obtained, the print may be removed to a bath 

 composed of 



Water . . . . . . 10 ounces. 



Hydrochloric acid . . ij drams. 



Any of the lemon colour left will here be cleared 

 away, and black and white tones only remain. 

 After five minutes in this bath the prints are 

 transferred to a similar but rather more dilute 

 bath for ten minutes, then to three baths of clean 

 water for ten minutes each, into the second of 

 which a few grains of sodium carbonate have been 

 added to neutralise any acid left in the prints. 



