74 //. J. (Tnii/xoii : 



permits of any siuLile portion of the section apparatus being 

 run separately : the remaining cords and j^ulleys being sta- 

 tionary. This effects a saving of power, and reduces the wear 

 and tear upon the iiiachine and belts or cords. The slicer, and 

 each grinder and the polisher, are hence directly connected 

 to the princi]tal shafting, which runs loosely through each 

 driving pulley, when the latter are not engaged. These pulleys 

 are thrown into action, each Ijy its own clutch, which is 

 operated by a loose coned sliding collar on the main shaft. 

 The sliding cone is moved directly from the work table by 

 means of a rod, to the lower end of which a lever handle bar 

 is rigidly screwed in a convenient position. At the top of the 

 rod is a forked lever with adjusting screws fitting a groove in 

 the sliding cone. By a twist of the handle bar below, the 

 cone is forced under the lever of the clutch, which tightly 

 engages the hub of the driving-wheel, and the lap or slicer, as 

 the case may be, is brought into immediate action ; the reverse 

 movement of course instantly disengages the clutch, and the 

 lap or slicer become stationary. The photograph (Plate XVI.), 

 which shows a portion of the main shaft, driving wheels and 

 clutches, will serve to make this portion of the mechanism 

 sufficiently clear. 



Connection between the driving wheel and each spindle, by 

 means of a leather cord, is easily effected, the latter passing 

 directly fmm wheel to s])indle Avith the aid of guide pulleys 

 only, these being secured to the under surface of the table. 



Provision was originally made for two speeds, the change 

 being effected by means of split imlleys on the spindle, which 

 can easily be removed if reipiii'ed : but this is seldom necessary. 

 A uniform speed of about !)S0 revolutions per mintite has been 

 foimd in every way satisfactory. 



An extremely useful adjunct to the rock slicer is to be found 

 in the small emery grindei- attached to the same bench (seen 

 to the left of Plate XV.) and driven in the same mannei". It i^ 

 speeded up to 2000 (or more) revolutions per minute, and has 

 been found most convenient for a variety of work for which 

 the larger machine is not so well adapted. It may be pro- 

 vided with various grinding and cutting wheels as well as 

 polishers and brushes, which tit it for use upon fossils, and the 



