No. 129.] 255 



in five years it extends two hundred feet, and is from twenty to 

 thirty inches in girth. This tree can, without being injured, 

 yield, by tapping, from fifty to sixty pounds weight of caoutchouc 

 in one season. 



" A curious contrast is exhibited in the tardy growth of the 

 tree from which gutta percha is obtained: This tree does not 

 come to its prime in less than from eighty to one hundred and 

 twenty years. The produce cannot be obtained but by the sacri- 

 fice of the tree. It is found in a concrete state between the bark 

 and the wood, after the tree is cut down, and it is in this condi- 

 tion that, having been scraped out, it is sent to our market. 

 When coagulated by evaporation or agitation, caoutchouc sepa- 

 rates from the ligneous portion of the sap of the trees which 

 yield it. The solid and fluid cannot afterwards be reunited, any 

 more than butter is capable of mixing with the milk from which 

 it is separated. Caoutchouc is a hydro-carbon. This chemical 

 character belongs to all varieties of the substance, and many 

 other vegetable constituents, though they differ materially in 

 physical qualities. Some specimens are harder than gutta 

 percha itself, while others never solidify, but remain in the con- 

 dition of bird lime or treacle. 



" A cube of two-and-a-quarter inches of caoutchouc was sub- 

 jected to a pressure of two hundred tons. Great heat appeared 

 to have been evolved, and the excessive elasticity of the 

 caoutchouc caused a fly wheel of five tons weight to recoil with 

 alarming violence." 



The Chairman stated the subjects for discussion to be subsoil 

 ploughing and draining. He requested Professor Mapes (who 

 had proposed those subjects,) to gives his views. 



Professor James J. Mapes, of New- Jersey. I cheerfully com- 

 ply with the request of the Chairman. In the first place, I call 

 attention of the Club to the effects of atmosphere upon the soil. 

 The changes which are caused in it by atmospheric influences 

 are obvious to some extent, but on a more close investigation, 



