232 USES OF CAOUTCHOUC. VEGETABLE OILS. 



the valuable properties of Caoutchouc, in the discovery of the 

 power of ether and naphtha* to dissolve it, without changing its 

 properties ; so that a kind of varnish may be thus formed, from 

 which, when it is spread over any surface, the dissolving fluid 

 (which is extremely volatile) will evaporate, leaving a very thin 

 coating of caoutchouc behind. It is in this manner, that the 

 waterproof fabrics are made, which are now so much employed 

 for cloaks, wrappers, &c.; and as these are also air-tight, they 

 may be used for air-cushions, mattresses, &c. The fabric con- 

 sists of two layers of cloth, which are varnished, each on one 

 side, and then passed between a pair of rollers with the var- 

 nished sides in contact- so that the two layers are pressed 

 closely together, a thin layer of caoutchouc existing between 

 them. Some idea of the great and increasing consumption of 

 this substance, new and useful applications of which are con- 

 stantly being discovered,^ may be formed from the fact that, 

 whilst in 1830 the quantity imported into England was more 

 than 52,0001bs. (nearly double that imported in the preceding 

 year), the consumption in the year 1833 was nearly 180,0001bs.; 

 and there can be little doubt that it has since increased in nearly, 

 if not quite, as rapid a proportion. 



370. The large number of Oils obtainable from plants, may 

 be divided into the fixed or fat oils, from which no vapour 

 passes off at the temperature of boiling water ; and the volatile 

 or essential oils, which give off vapour at or below that tempe- 

 rature. The latter are the sources of all the odours, diffused so 

 widely through the vegetable kingdom ; and furnish, also, some 

 materials of great importance in the arts of life. The fixed oils 

 are all obtained by pressure from the fruits or seeds of plants, 

 especially those of the Nut kind, all of which contain it in 



* This fluid is obtained in England from the tar, which passes over with the 

 gas now so universally employed, when coal is heated in closed retorts. . 



+ A patent has lately been obtained for the employment of solid Caoutchouc in 

 saddles and horse-collars. Two objects are here attained by it; the much 

 increased comfort of the horse, by the equal diffusion of pressure over the surface, 

 by which galling is prevented; and the preservation of the padding beneath, by 

 protecting it from being saturated (as it otherwise frequently is) with the perspira- 

 tion of the animal. 



