CH. IV] 



EXPERIMENTS FOR INTERPRETATION 



123 



the advice of Beale, p. 248, and examine first with a low power then 

 with a higher power; mounted dry, then in water; lighted with re- 



TIG. 74. COMPARISON OCULAR FOR PLACING HALF THE FIELDS OF Two 

 MICROSCOPES SIDE BY SIDE. (R l R 2 ). 



(Bausch & Lomb Optical Co., from Chamot). 



T l To fit into the tube of the left microscope. 



T 2 To fit into the tube of the right microscope. 



P 2 Prism to reflect the beam from the right microscope to the prism R 2 , 

 whence it is reflected up through the ocular (O) into the right half of the field 

 shown above in the face view. 



P l R l The prism and left half of the field shown in face view in the diagram 

 at the top. 



fleeted light, then with transmitted light, the following: potato, wheat, 

 rice, and corn starch (easily obtained by scraping the potato and the 

 grains mentioned); bread crumbs; portions of feather (portions of 

 feather accidentally present in histological preparations have been 



