22 GOODYEAR ON GUM-ELASTIC. 



PROPERTIES OF THE NATIVE GUM. 



Native gum, or Caoutchouc, does not lose any of its valuable 

 properties, by age or exposure to moisture. It is not materially 

 injured, (although it is penetrated and considerably softened,) 

 vv^hen immersed long in water. It is, however, soon damaged 

 by exposure to a hot sun, which is the only injury those who are 

 engaged in gathering or dealing in it, need to guard against, 

 except that of getting foreign substances mixed with it. When 

 left to coagulate with the whey, or sap, it contracts a tainted odor, 

 and filthy appearance, and some persons have rejected it, on this 

 account, supposing it to be damaged, when it is not. This is dis- 

 tinct from the natural odor of the gum, treated of in another 

 place, and does no harm, as it is dispelled by the heat of the 

 vulcanizing process. 



The air- and water-proof quality of gum-elastic is one with 

 which the pubhc are well acquainted. 



Great adhesiveness is another remarkable property of this 

 substance. Where two surfaces of the gum are brought in 

 contact, they are readily and solidly united, by the application of 

 heat and pressure. When in large masses, after being sometime 

 exposed to the atmosphere, it appears to be inadhesive, and inde- 

 structible, but when spread out into thin layers, on cloth or in 

 sheets, it is quite the opposite. When any two surfaces of it 

 are brought in contact, if perfectly clean, they adhere together 

 even without pressure, so that they cannot be separated. It was 

 losing sight of this fact, or not understanding it, that led to such 

 mistakes, and losses in the early attempts to manufacture the 

 article, in America. In cold, or even moderately cold weather, 

 it becomes so stiflf and hard, when of any considerable thickness, 

 as to render it unfit for any use, where flexibility is required, 

 without first being warmed. 



The most remarkable quality of this gum, is its wonderful elas- 

 ticity. In this consists the great difference between it, and all 



