134 GOODYEAR ON GUM-ELASTIC. 



ant supply of coal for fuel, of iron among the metals, for tools 

 and implements, and in the abundance and cheapness of glass 

 ware. What is also remarkable is, that it appears that various 

 substitutes for things in use are frequently discovered just at the 

 time when the articles become scarce ; and what is yet more 

 remarkable, the substitutes which are discovered often answer a 

 better purpose than the article originally used. 



This remark will apply particularly to coal, as a substitute for 

 wood ; to vegetable oils, gas, and lard oil, as substitutes for whale 

 oil ; and why may we not extend the comparison to gum-elastic, 

 and say that by this discovery we have received a vegetable 

 leather as a substitute, to some extent, for animal leather, gum- 

 elastic vellum for parchment, and for certain uses at least, such 

 as umbrellas, oil-silks, &c., a vegetable silk for that spun by 

 insects ? 



N. B. A distinctive and singular feature in this discovery, 

 and one that is deserving of special notice, is this, that heat, 

 which is one of the two principal agents which produce the 

 desired result, melts every kind of caoutchouc at a compara- 

 tively very low temperature. The heat of the sun's rays will 

 melt them, while, with the presence of the other agent, that of 

 sulphur, the great change is wrought in the caoutchouc, and the 

 improvement is completed, at the high temperature of nearly 

 300°. 



