CAOUTCHOUC, OR INDIA RUBBER. 383 



established, its vegetable origin was doubted by a few who considered 

 its nature to partake more of the mineral than of the vegetable: but 

 Dr Koxburgh, a subsequent investigator of this product, fully confirmed 

 M. De la Condamine's statement that the substance was the inspissated 

 juice of a tree, and at once dispelled those somewhat singular notions by 

 a careful enumeration of the then known trees which yielded it. 



The botanical history of caoutchouc is in itself most interesting. Its 

 classification is easy, though it is still doubtful whether all its sources 

 have yet been ascertained. The explorations of modern travellers make it 

 probable that other sources, apart from those on which we have hitherto 

 relied for our caoutchouc supply, exist, and promise an inexhaustible yield. 

 To America and the East Indies the early manufacturers were indebted for 

 their supplies of caoutchouc ; and it is an interesting and most significant 

 and hopeful fact, that although the application of the demand for the 

 material has made rapid progress, the supply has in no one instance fallen 

 short of the demand, either in price or quality. On the contrary, the better 

 kinds of caoutchouc — i.e., "Para" and "Bottle" — equal in bulk and quality 

 the supply of any former period. Much of this is to be attributed to 

 greater care consequent upon experience, and the interposition of European 

 agency in the collection and treatment of the " sap," preparatory to con- 

 solidating and moulding it for export. Gradually, however, as the demand 

 increased, fears were manifested that the supply would fall short, and 

 ultimately cease altogether : and this probability was the more threatening, 

 as the value of the gum had been fully tested and appreciated. Such fears 

 promoted further search and investigation, in order to discover other 

 sources. The supply, however, notwithstanding all anticipations to the 

 contrary, did not fall off. It was soon found that caoutchouc was not 

 confined to a few districts in America and the East Indies, but that 

 Australia,* Southern China, the Mauritius, Madagascar, Java, Singapore, 

 Penang, Assam, and Africa added their supplies in such quantities as to 

 dispel the apprehensions which had existed ; and, as exploration proceeded, 

 it was found that the whole of the islands dotting and studding the 

 Indian Archipelago abounded in forests of caoutchouc-yielding timber. 



Let lis here remark that caoutchouc exists exclusively in what is termed 

 the "milk sap" or "juice" of plants, varying in quantity with the plant 

 yielding it, and its geographical position in the tropics. Plants yielding 

 this milk-sap are doubtless to be found on every portion of the earth's 

 surface, obeying the general law governing vegetable life — viz., increased 

 productiveness in proportion to their vicinity to the tropics. Humboldt, 

 in the first edition of his ' Aspects of Nature,' notices this fact, " that the 

 milk-juice of plants increases as they approach the tropics." 



Caoutchol^c, on the whole, is a substance far more widely diffused among 

 plants than is generally considered. In addition to the two chief families 

 which yield the caoutchouc of commerce, the Artocarpacese and the 

 Euphorbiacese, caoutchouc has been found in the sap of plants belong- 



* The Ficus Australia abounds in the northern part of Queensland. 



