S:^9 — 



r 



214 SOODYEAE ON GUM-ELASTIC. 



softer, buffalo-horn and whalebone ; while they possess, in 

 general, more durable properties than any of the substances 

 above named, except marble, and they are even more sub- 

 stantial than that, in some respects ; because, in all degrees of 

 hardness, they have a great degree of toughness or tenacity, and 

 the property of retaining the shape into which they have been 

 moulded and heated. 



Glass and the metals are too heavy for many small or hght 

 articles of convenience, too much so for some for which they 

 are used Bone and horn are worked and finished with diffi- 

 culty, while this material is worked and finished simply by 

 moulding. Whalebone and ivory are every day becoming more 

 scarce, and these also are manufactured with great difficulty 

 and great waste, in comparison vi^ith this material. 



CAOUTCHOUC ENAMEL. 



This term is applied to this substance, because it is the hard- 

 est of all the hard heated compounds, and because the ingredi- 

 ents differ materially from those of the substances which are 

 hereafter noticed as ivory and whalebone. 



The process by which they are all made is the same. The 

 principal difference is in the addition of a considerable portion of 

 oxide of magnesia, iron, white lead, or other metal, with a larger 

 proportion of sulphur in compounding the marble. It is some- 

 what more brittle than the India rubber ivory, and does not an- 

 swer for all purposes so well, but it will unquestionably be found 

 to answer, in many cases, where a substance is desired which is 

 very hard, and yet not so heavy or brittle as porcelain or mar- 

 ble ; it is not yet made so white as porcelain, but admits of col- 

 oring, moulding, and variegating, like the other hard compounds. 

 The most important uses of this enamel are probably the plating 

 or covering of iron furniture, coach and harness mountings, &c. 



