ELEMENTARY PHOTO-MICROGRAPHY. 25 



microscope in its horizontal position about a foot 

 away from the screen, first having swung the mirror 

 0n one side and removed the substage condenser. 

 Put in the A eyepiece and a 2in. objective for a 

 start, and focus on to a suitable slide on the stage 

 ef microscope. Then lower the room lights and 

 bring round the oil lamp and bull's-eye, and adjust 

 them so that a set of horizontal parallel rays is 

 projected through the slide to be examined into 

 the tube of microscope. 



A disc of light will immediately appear on the 

 cardboard, but probably brighter in one part than 

 another, in which case the light, or the bull's-eye, 

 or both, should be slightly moved till the illumina- 

 tion of the disc is perfectly uniform in brightness. 



Having got this effect, see that the object is 

 in the centre of the field, when a little focussing will 

 bring it into sharpness and make it visible to all. 



If the substage condenser and a higher power 

 be used, the cardboard may perhaps have to be 

 brought nearer to the eyepiece, and a sheet of 

 ground-glass between the light and the substage 

 condenser will often make a wonderful difference 

 in securing even illumination. The only difference 

 betwixt enlargements made in this manner and 

 pictures in photo-micrography is that for photo- 

 graphic purposes the magnified image is received 

 on the ground-glass screen of a camera instead of 

 on a cardboard sheet. 



