ULTRAMICROSCOPES 



117 



part in the forma- 

 tion of images, 

 although the illu- 

 minating rays in- 

 clude a range of 

 high aperture, i.i 

 to 1.35. There is 

 thus obtained the 

 greatest brilliancy 

 of image upon the 

 darkest of back- 

 grounds. 



Although many 

 different ultracon- 

 densers are obtain- 

 able, space forbids 

 a consideration of 

 more than two 

 types: the cardi- 

 oid condenser of 

 Siedentopf as made 

 by Zeiss, and the 

 ultracondenser of 

 Jentzsch as made 

 by Leitz. 



The Cardioid 

 Ultramicroscope 

 consists of an or- 

 dinary compound 

 microscope M, Fig. 

 57, into whose sub- 

 stage ring the car- 

 dioid condenser C 

 is introduced and 

 held in place by 

 the clamping screw 

 t. A thin film of 



