224 



PHOTO-MICROGRAPHY 



\_CH. VIII 



objects. For smaller objects a Steinheil lens combination gives a more bril- 

 liant light and one also more nearly achromatic. For high power work all are 

 agreed that nothing will take the place of an achromatic condenser. This may 

 be simply an achromatic condenser, but preferably it should be an apochroma- 

 tic condenser. Whatever the form of the condenser it should possess dia- 



Otiilir Ho 2 



Fig. 173. Compensation Oculars of Zeiss, with section removed to show 

 the construction. The line A- A is at the level of the upper end of the tube[of 

 the microscope while B-B represents the lower focal points. Zeiss recommends 

 the use of the compensation oculars if one desires a greater magnification than 

 the projection oculars give. 



Fig. 174. Bull's eye lens and holder. (Bausch & LomhOpl. Co.) 



