This
seems the most promising of the home-grown plants and, until artificial
rubber can be made profitable, gives us the only chance of being in part
independent of oversea supply.
There are various other gums found in nature that can for some purposes
be substituted for caoutchouc. Gutta percha, for instance, is pliable
and tough though not very elastic. It becomes plastic by heat so it can
be molded, but unlike rubber it cannot be hardened by heating with
sulfur. A lump of gutta percha was brought from Java in 1766 and placed
in a British museum, where it lay for nearly a hundred years before it
occurred to anybody to do anything with it except to look at it. But a
German electrician, Siemens, discovered in 1847 that gutta percha was
valuable for insulating telegraph lines and it found extensive
employment in submarine cables as well as for golf balls, and the like.
Balata, which is found in the forests of the Guianas, is between gutta
percha and rubber, not so good for insulation but useful for shoe soles
and machine belts.
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