ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 



669 



The scale, with two graduations, is adapted to the operations for either 

 RMi or RMii, or in the case of changing from the one to the other. 



5. Each of the knife-rests (fig. 98) has a notch and three screws for 

 receiving and fixing the knife ; the small screws are for determining the 

 most favourable obliquity for the knife, and the milled-head acts as a 

 clamp. As efficiency is promoted and wear and tear diminished by 

 choice of proper materials, the author introduces the best cast-steel for 

 the ironwork; instead of soft brass, he uses a hard wear-resisting 

 bronze-alloy. 



r - v ■ / \ v / 



Fz Fi 



Fig. 102. 



Fig. 103 shows an arrangement for ensuring thorough lubrication 

 and for preventing shakiness of the working parts. The figure is a 

 section through the region of the axial bolt T, about which the working- 

 lever F turns. The sector G is not, as usual, directly rotatory about 

 this bolt, but rotates with a long flange, G b, about a steel box, U. 

 This box is thickened at its base, and rests on the base-plate. A flange 

 on the bolt T fits on the thickening and keeps U firmly pressed down. 

 The nut Tm below the base-plate tightens all up. The axis of the 

 bolt T coincides with that of the box U. In this way the working- 



