ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 



839 



glance it can be seen whether it is in contact or not. The layer of 

 immersion liquid allows the grazing rays to pass even when the nrst 

 lens is nearly in contact with the slide. This arrangement is very 

 useful, and will be popularized more and more as an adjunct in the 

 use of very high power objectives." 



Fto. 158. 



Nachet's Microscope with fixed Revolver for Objectives.— This 

 Class Microscope (fig. 158) represents another attempt * to cope with 

 the tendency of French students to unscrew the objectives of Micro- 



* Sec this Journal, v. (1885) p. 514. 



