1 f>,x 



ment can be made after the high power objective 

 is attached. 



In the simple form, pin hole cap is usually not 

 provided. To verify correct centering two easy 

 methods may be followed. 



1. Use a 2 inch objective and focus through the 

 condenser onto the diaphragm, whicli is reduced to its 

 smallest opening. 



2. Use a f or f- inch objective and bring to its focal 

 point ; remove eyepiece and look through the tube, 

 keeping the eye in center, when the small opening of 

 diaphragm will be seen sharply defined. 



This opening in diaphragm may be enlarged to 

 the full aperture of objective so that the margin 

 of opening in the diaphragm will just coincide 

 with that of the back lens of objective. 



Centering the Illumination. --This is fully as 

 important as centering the condenser, for it is of 

 little avail to have a centered condenser when the 

 projected beam of light is not centered. This 

 depends upon the source of light and position of 

 mirror and when it is remembered that the mirror 

 may be so adjusted as to give all gradations of 

 oblique illumination from the central to the limit 

 of aperture, the necessity for accurate adjustment 

 becomes apparent. 



Attach f or f- inch objective ; open diaphragm to 

 full extent and focus upon the minute image of 



