196 METHODS OF MICROSCOPICAL RESEARCH. 



and well swilled with water from a jug or tap. It 

 is then to be placed face upwards in the dish of 

 " hypo," and left there five minutes or so, until all 

 trace of milkiness disappears from the back of the 

 plate. It may then be removed from the "hypo," 

 again swilled with water, and if the weather is not 

 hot, and the plates are known to have no tendency 

 to frill, it may be placed in a dish of water and left 

 to soak. This soaking must be continued for about 

 six hours, in several changes of water. The plate 

 may then be stood on end to dry. Heat must not 

 be applied to hasten the drying, or it will cause the 

 gelatine to dissolve. From the time the plate comes 

 from the hypo it is insensitive to light,, and, indeed, 

 it may be taken into the light and fixed there as 

 soon as the developer is washed off, without any 

 considerable harm happening to it, but it is best not 

 to expose it to light until it is fixed. The photo- 

 grapher cannot be sure of the character of his 

 negative until it is fixed, and during this process it 

 will undergo a remarkable change, it will lose its 

 translucency and become transparent. If the 

 exposure and development have been correct, the 

 highest lights will be so dark as to make it very 

 difficult to distinguish even bright objects through 

 them, while the deepest shadows should be almost 

 as clear as the plain glass, and the half tones full of 

 detail. 



If on the first application of B, the details come 

 up with undue rapidity and then begin to fade 

 away, the plate has been over-exposed, and the 

 developer must be instantly poured back into the 

 beaker and the plate flooded with water while 20 to 

 30 drops of C, according to the amount of over- 



