INSTRUMENT HANDLES. 179 



SCALES AND RULES. 



Mathematical scales and carpenter's rules are manufactured 

 of caoutchouc whalebone and ivory, as substitutes for boxwood 

 and ivory. Although they are not yet made as white as ivory, 

 they are preferable to either boxwood or ivory on other accounts, 

 They are stronger and not so liable to warp or crack as ivory or 

 boxwood. They are manufactured with much greater economy 

 in the saving of labor and material. The mountings are se- 

 curely set in while they are being vulcanized in the mould. 

 They are also graduated by the mould during the same process. 

 By which process the cost of manufacture is very trifling com- 

 pared with that of other rules, as heretofore. 



INSTRUMENT CASES. 



These are made of caoutchouc whalebone. The two parts 

 moulded, each of them, in one entire piece. 



They are further improved by a hinge of gum-elastic com- 

 pound, and a cushion or packing of gum-elastic fabric around 

 the edge, which makes them quite air-tight, so that the instru- 

 ments contained in them are prevented from rusting. See 

 plate , fig. 



INSTRUMENT HANDLES. 



Superior handles are manufactured from caoutchouc ivory 

 and whalebone, for various kinds of surgical, dental, etching, 

 drawing, and engraving instruments. The shanks of the in- 

 struments being made rough, the handles are formed on them, 

 and shaped in moulds when vulcanized, whereby there is great 

 economy in the manufacture ; and a decided improvement is 

 made in the tools by the handles being secured so perfectly that 

 they cannot come off, or be taken off without destroying them. 

 See plate , figs. 



