466 PREPARATION, MOUNTING, AND COLLECTION OF OBJECTS 



Fig. 395 presents an object-holder intended to analyse by diversified 

 section objects which are wedged or fan-shaped in form on a fixed 

 axis, but may be applied to other purposes. 



B is a prism-shaped, semicircularly bent bar, moving in the slot 

 F F 1 ; at b and b l the jaws occupy the position common to those of 

 the ordinary form. 



FIG. 395. Object-holder for analysis by diversified section. 



On the circumference of B a spiral is cut, which becomes slightly 

 visible at g ; into this spiral a screw passes at H, which is turned bv 

 the milled head S, which can alter the position of the arc to the 

 horizontal to the extent of 1 mm. ; and the amount of the change of 

 position can be read off on the graduated circle K. 



In a fixed position the middle of this section-holder is the plane 

 of action of the knife. If an object be fixed in the jaws so that the 



FIG. 396. Cylinder for u 



fixed axis of it lies in this plane, it will only be required that the 

 screw S be brought into action to obtain wedge-shaped sections of 

 whatever thickness is required, which will all be made in this axis. 



The set of cylinders which may be used with these and other 

 jaws is represented in fig. 396 : b y is the cylinder, G the compressing 

 screw for it, the block W being held in the jaws. 



The object-slide with its vernier may be sliddeii up the incline by 



