MAKING SECTIONS OP WOOD, ETC. 335 



CHAPTER XII. 



ON MAKING SECTIONS OP WOOD. 



Foe this purpose we must be provided with an instrument 

 termed the Cutting machine, which consists of a plate of metal, 

 on which a knife or razor is made to slide, and the wood to be 

 cut is firmly wedged into a triangular or other tube, and is 

 raised above the surface of the tube by a very fine screw, as 

 high as the thickness of the section required. The first instru- 

 ment of this kind was invented by Adams, about the year 1770, 

 and was subsequently improved by Mr. Gumming ; it is de- 

 scribed and figured in the microscopical essays of the younger 

 Adams, and is of the same kind as that employed by Mr. Cus- 

 tance, " who was unrivalled," says Adams, " in his dexterity in 

 preparing and accuracy in cutting thin transverse sections of 

 wood." In subsequent times other instruments have been 

 contrived for the same purpose, some provided with knives 

 which move circularly, others with knives fixed in a strong 

 frame-work of metal, whilst, in not a few, the cutting is 

 performed by a rs^zor of the ordinary kind, or one ground 

 perfectly flat on one side. A very excellent machine for this 

 purpose, which the author has been in the habit of using for 

 many years, and can, therefore, strongly recommend, is shown 

 in fig. 224 ; it consists of a block of Spanish mahogany, into 

 which are fastened four strong brass pillars that support a flat 

 table of the same metal, eight inches long, three wide, and 

 three-tenths of an inch thick, having a raised edge screwed to 

 one of its sides; to the under surface of the middle of this table, 

 and nearly close to the side opposite to that having the raised 

 edge, is screwed a stout tubular piece of brass, c, which passes 

 through the table and projects about a quarter of an inch 

 above its upper surface ; into this tube is fitted accurately a 

 cylindrical piece of brass, /, having a hole, g, about five-eighths 

 of an inch square, extending throughout its entire length. 

 This cylinder is capable of being raised by a screw with forty 



