56 ELEMENTARY PHOTO-MICROGRAPHY. 



his individuality will be manifested. The iris 

 diaphragm will sometimes be needed ; at other 

 times it may be the polariscope, especially for 

 crystals, or perhaps the colour screen must be 

 employed. Which method and which colour 

 screen will only rightly be selected after experi- 

 ence has been gained. If the worker prepares 

 his own object, he can often stain it to bring out 

 its details. However, all these matters will have 

 to be dealt with separately. 



Commencing with a simple object and the lowest 

 power, we first set up the baseboard, with lamp, 

 microscope, and camera duly placed in position 

 (see fig. 14), but as an object may be photographed 

 by direct transmitted light, reflected light, and with 

 dark ground or light ground, we will first consider 

 transmitted light and a light background. 



If the reader has tried the simple experiment 

 of getting an enlarged picture on a sheet of white 

 cardboard, as described in Chapter II., he will 

 have no difficulty in obtaining the image on the 

 ground-glass screen of the camera. 



Having placed the object on the stage of the 

 microscope, it is focussed with the A eyepiece, the 

 camera and sliding block having been removed for 

 this purpose. No substage condenser is needed 

 for powers lower than iin., but for higher powers 

 it is indispensable ; therefore, instead of critical 



