ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
105 
The requirement of convenient adjustability in height is satisfied by 
the apparatus being attached to the body-tube by means of a clamping 
ring, while the adjustment from side to side is effected by the prism, 
II 
Fig. 12. 
Fig. 13. 
H 
P 
together with the cap and smoked glass disc, being centered from front 
to back by means of a screw H working through a spring socket, and 
from right to left by means of a second screw L, against which works a 
counter-spring not seen in the figure, 
