ELEMENTARY PHOTO-MICROGRAPHY. 41 



Fig. ii is a board about 5ft. long, 8in. wide, 

 and lin. thick. Fig. 12 is the end view showing 

 flanges, say, 2in. deep. The sliding block (fig. 13) 

 slides freely between these flanges, and is fixed by 

 the thumbscrews. The camera, microscope, and 

 lamp are seen in position in fig. 14. 



FIG. ii. FIG. 12. FIG. 13. 



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 then be slid over every part of 

 the screen, after the projected image is thrown 

 upon it, to ascertain whether each part of the 

 object is equally in focus. 



When high powers of the microscope are em- 

 ployed, the rough side of the glass should have a 



