India Rubber, Or Elastic Resin. Is a substance produced from the syringe-tree of Cayenne and other parts of South America, and possessed of the most singular properties. No substance is yet known which is so pliable, and at the same time so elastic; and it is farther a matter of curiosity, as being capable of resisting the action of very powerful menstrua. M. de la Condamine says it oozes out, under the form of a vegetable milk, from incisions made in the tree; that it is gathered chiefly in time of rain, because it flows then most abundantly. The means employed to inspissate and indurate it, are kept secret. By inspissate is meant to thicken, and by indurate to harden, which M. Bomare says it does gradually, by being exposed to the air. The Indians make boots of it, which water cannot penetrate, and which, when smoked, have the appearance of real leather. Bottles are also made of it, the necks of which are fastened to hollow reeds, so that the liquor contained in them may be forced through the reed or pipes by pressure. One of these filled with water is always presented to the guests at their entertainments, who never fail to make use of it before eating. Flambeaux, an inch and a-half in diameter, and two feet long, are likewise made of this resin, which give a beautiful light, have no bad smell, and burn twelve hours. A kind of cloth is also prepared from it, which the inhabitants of Quito apply to the same purposes as our oilcloth and sail-cloth. It is formed, by means of moulds, into a variety of figures for use and ornament. The process is said to be thus: - The juice, which is obtained by incision, is spread over pieces of clay formed into the desired ornamental shape, and as fast as one layer is dry, another is added, till the whole be of a proper thickness. It is then held over a strong smoke of vegetables on fire, whereby it hardens into the texture and appearance of leather, and before the finishing, while yet soft, is capable of receiving any impression on the outside, which remains ever after. Many attempts have been made to dissolve it so as to make it assume different figures, with equal ease as when it was in its original state, running from the tree. Mr. Macquer tried oils, turpentines, spirits of wine, the milky juice of other vegetables, heat, etc, but none of these was capable of dissolving it. At last he tried ether, which perfectly dissolved it, without any other heat than that of the atmosphere. It was then transparent, and of an amber colour.
A resin, similar to this, was discovered some years ago by Mr. Poivre, in the isle of France. Some kinds of this gum have been dissolved by other methods.