336 



MANIPULATION. 



threads in the inch, the head of which, b, is divided into twenty 

 five parts ; the divisions are cut so deep, that a thin wedge 





I I 



Fig. 224. 



shaped piece of steel may be pressed firmly into any of them 

 by the spring, a, with which it is connected ; this contrivance 

 answers two purposes, one as a micrometer for determining 

 how high the cylinder must be raised to cut the finest section, 

 and the other for preventing the screw from being moved. 

 A strong brass frame, of the shape shown in the upper part 

 of the figure, and of nearly the same thickness as the table, 

 has a knife, e, ground perfectly flat on its under surface, firmly 

 fixed to it by two strong screws, d d; this frame, with its knife 

 arranged in the manner seen in the figure, is made to slide 

 backwards and forwards smoothly upon the upper surface of 

 the table. The wood about to be cut is driven very tightly 

 into the square hole, g, in the cylinder, yj and should be allowed 

 to project about an eighth of an inch above it. The cylinder 

 being replaced within the tube, c, it wiU be found that when 

 the frame is pushed forwards the edge of the knife will pass 

 obhquely over every part of the surface of the wood, and as 



