MAKING SECTIONS OF BONE AND TEETH. 327 



section from the glass; this is resdily effected by dropping the 

 slip of glass into the stoppered bottle containing ether, which, 

 in a very short space of time, will dissolve all the balsam, when 

 the section will drop off; it may then be removed from the 

 ether, and when dried is ready for being permanently mounted. 

 It win now be seen why a slip of glass of a particidar length 

 and breadth was recommended at the commencement, it has 

 many advantages over either longer or shorter strips; in the first 

 place, if the section should be thicker on one side than the 

 other, the glass can be tilted a little, so that the side which is 

 the thickest may be rubbed the most, and in a short time an 

 uniform degree of thinness will be obtained ; secondly, it is by 

 far the best plan to keep ether in a bottle with a stopper not 

 much exceeding half-an-inch in diameter, as in larger bottles 

 the stoppers seldom fit so nicely as to prevent evaporation ; 

 into the small bottles the slips of glass previously described 

 will readily drop, and the ether need not more than half fill 

 the bottle, for so long as it reaches as high as the section, 

 the desired object will be obtained ; when, however, the stock 

 is reduced so low that it will not reach the section, one end of 

 the slip of glass may be cut off with a diamond, and only a 

 small quantity of ether wiU then be necessary. 



If it be required to make sections of fossil bones that are 

 too hard to be cut with a saw, the apparatus employed by the 

 lapidary must be had recourse to ; this consists of a thin iron 

 wheel, the edge of which is charged with emery, or with 

 diamond dust ; after the section has been made, it is then to be 

 cemented to a piece of glass and polished on both surfaces, 

 the material used for the cutting being a fluid known as oil 

 of brick. The ordinary wheel employed by the lapidary runs 

 horizontally, and is turned by the hand ; an apparatus of the 

 same kind, but used by the jeweller, consists of a small steel 

 or copper disc, turned by a foot-wheel ; one or both of these 

 will be required by those who wish to devote much attention 

 to the structure of fossil bones and teeth. It is usual to mount 

 such sections on pieces of plate-glass, without any covering of 

 Canada balsam or thin glass over them ; if they have a polished 

 surface, their structure can be admirably made out. 



