106 ELEMENTARY PHOTO-MICROGRAPHY. 



All these preparations being made, the dark 

 slide is opened and a plate put in the dish, gelatine 

 side up, taking care not to touch the gelatine side 

 with the fingers. Plates must always be lifted by 

 the edges. If the dark slide has been kept clean, 

 there is no advantage in first brushing the slide 

 with a camel-hair flat brush or with velvet, as the 

 danger of leaving dust specks on the plate is as 

 great as getting them from the dark slide. The 

 plate should not be washed before development. 



The developer must be swept over it quickly 

 in such a way that no part of the plate is left dry, 

 even for a moment, and the dish gently rocked to 

 keep the solution constantly on the move all over 

 the surface of the plate. If the developer be 

 insufficient in quantity, dry places will be noticed 

 on the plate, over which the developer will not 

 readily flow. This should not be allowed. The 

 developer should be used at a temperature of about 

 60 F. In very cold weather this is important, or 

 the action, if there is any at all, will be slow. 



With the thermometer and developer at freezing 

 point, it is possible for a properly exposed plate 

 to show no signs of any image for quite a long 

 time, whereas on warming the solution develop- 

 ment will proceed in a normal manner. 



Boiled water that has gone nearly cold may be 

 used, commencing with less than the full quantity 



