ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 



353 



polariser. R is the prism with its film grating, and G- a plane-parallel 

 glass plate for protecting the prism chamber. By means of a lever the 



Fia. G3. 



prism grating may be moved aside and a film-grating substituted for it. 

 The whole is applied under the stage like a substage condenser. 





Fig. 64. 



63 shows the arrangement of levers for detaching- the nicol N, 

 the film-grating S, and the prism-grating R. 



Fig. 



