sufficiently centered by the maker for all ordinary 

 requirements but there should be provision to center 

 it in case of disarrangement. 



In the more complete apparatus adjustment screws 

 should be supplied. These provide a ready means of 

 centering and when once the correct position with one 

 objective is determined it will not require any further 

 attention. 



To verify correct centering two easy methods may 

 be followed : 



I. Use a 2 inch objective and focus through the 

 condenser onto the diaphragm, which is reduced to its 

 smallest opening. 



II. Use a 2-3 or I inch objective; focus upon 

 upper surface of condenser or upon an object which 

 should then be removed; elevate objective with coarse 

 adjustment until a dimly defined dark spot appears in 

 the field and with proper focusing is about i-j of the 

 diameter of the field. 



Centering of the condenser does not imply that the 

 cone of illumination is also centered and it is fully as 

 important to secure the correct conditions in one as it 

 is in the other. 



Centering the Illumination. The mirror may 

 be so adjusted that the light will be directed toward the 

 periphery of the condenser and when lamplight is used 



1 60 



