ILLUMINATION WITH CONDENSER. 



Up to this point the matter of illumination has 

 been treated in its most simple torm with mirror 

 only, as most instruments are of the simple type, 

 but we must now consider the substage condenser, 

 which is a most valuable adjunct to the micro- 

 scope. While skillful treatment of the microscope 

 will go far toward obtaining good results, it will in 

 many investigations not suffice. Furthermore the 

 condenser will give results with ease which without 

 it involve effort and skill. 



Purpose of the Condenser.- -The purpose of 

 the condenser is not only as its name implies, to 

 condense light, but is more especially to illuminate 

 the object with a cone of light having an angular 

 aperture equal to that of the objective used and 

 which is absolutely unattainable with a mirror 

 only, as well as to provide means for controlling 

 the amount and character of the illumination to 

 suit the various conditions of work. 



Abbe Condenser. The history of substage 

 condensers is very unique and interesting and 

 shows, how from having been the subject of no 

 end of condemnation, which for many years it 



