ELEMENTARY PHOTO-MICROGRAPHY. 25 



thumbscrews. The camera, microscope, and lamp 

 are seen in position in fig. 9. 



Fig. 9. 



For a focussing glass any of the ordinary type will 

 do, and when once set to suit the sight of the owner, 

 will need no further alteration. A mark with lead 

 pencil must be made on the rough side of the 

 ground-glass screen, and then, turning it over, the 

 focussing glass is put in contact with the smooth 

 side, the lens being screwed to and fro until the 

 pencil mark is clearly in focus. It is important to 

 rest the foot of focussing tube upon the glass whilst 

 making the adjustment. The focussing glass may 



