190 



SECTION-INSTRUMENT. 



flat surface. At one side is seen a small milled -head, which acts 

 upon a 'binding- screw,' whose extremity projects into the cavity 

 of the cylinder, and serves to compress and steady anything that 

 it holds. A cylindrical stem of wood, a piece of horn, whalebone, 

 cartilage, &c. , is to be fitted to the interior of the cylinder, so as 

 to project a little above its top, and is to be steadied by the 

 1 binding-screw ; ' it is then to be cut to a level by means of a sharp 

 knife or razor, laid flat upon the table. The large milled-head is 

 next to be moved through such a portion of a turn as may very 

 slightly elevate the substance to be cut, so as to make it project in 

 an almost insensible degree above the table ; and this projecting 

 part is to be sliced-off with a knife previously dipped in water. 



Fig. 95. 



Section-Instrument. 



The best knife for this purpose is a razor, ground flat (instead of 

 concave) on one side, but having still a concave surface on the 

 other ; the flat side is to be laid downwards upon the table ; and 

 the motion given to the edge should be a combination of drawing 

 and pressing. (It will be generally found that better sections are 

 made by working the knife from the operator, than towards him.) 

 "When one slice has been thus taken off, it should be removed from 

 the blade by clipping it into water, or by the use of a camel-hair 

 brush ; the milled-head should be again advanced, and another 

 section taken ; and so on. Different substances will be found both 

 to bear and to require different degrees of thickness ; and the 

 amount that suits each can only be found by trial. It is advan- 

 tageous to have the large milled-head graduated, and furnished 



