CAOUTCHOUC 693 



25 10' and 27 20' of north latitude, and between 90 40' and 95 30' of east longi- 

 tude. It occurs on the slopes of the hills up to an elevation of probably 22,500 feet. 

 This tree is of tho Banyan tribe, famed for its pillared shade, ' whoso daughters grow 

 about the mother tree,' which has furnished the motto, Tot rami, quot arbores, to tho 

 Koyal Asiatic Society. Species of this genus afford grateful shade, however, in the 

 tropical regions of America as well as Asia. 



Many species of other trees yield a milky tenacious juice, of which bird-lime has 

 been frequently made ; as Artocarpus integrifolia and Lakoocha, Ficus indica and 

 religiosa, also F. Tsiela, Eoxburghii, glomerata, and oppositifolia. From somo of these 

 an inferior kind of caoutchouc has been obtained. 



The juice of the Ficus elastica of Chardwar is better when drawn from the old than 

 from the young trees, and richer in the cold season than in the hot. It is extracted 

 by making incisions a foot apart, across the bark down to the wood, all round the 

 trunk, and also the large branches, up to the very top of the tree : the quantity which 

 exudes increasing with the height of the incision. The bleeding may be safely repeated 

 once every fortnight. The fluid, as fresh drawn, is nearly of the consistence of cream, 

 and pure white. Somewhat more than half a maund (42 Ibs.) is reckoned to be the 

 average produce of each bleeding of one tree ; or 20,000 trees will yield about 12,000 

 maunds of juice ; which is composed in 10 parts, of from 4 to 6 parts of water, and, of 

 course, from 6 to 4 parts of caoutchouc. The bleeding should be confined to the cold 

 months, so as not to interfere with or obstruct the vigorous vegetation of the tree in 

 tho hot months. 



Mr. Griffith says, that the richest juice is obtained from transverse ineisions made 

 into the wood of the larger reflex roots, which are half exposed above ground, and that 

 it proceeds from the bark alone. Beneath the line of incisions, the natives of Assam 

 scoop out a hole in the earth, in which they place a leaf of the Phrynium capitatum 

 (Linn.), rudely folded up into the shape of a cup. He observes that the various 

 species of Tetranthera, upon which the Moonga silkworm feeds, as also the castor-oil 

 plant, which is the chief food of the Eria silkworm, do not afford a milky caoutchouc 

 juice. Hence it would appear that Dr. Eoyle's notion of caoutchouc forming a neces- 

 sary ingredient in the food of silkworms, and being ' in some way employed in giving 

 tenacity to their silk,' seems to be unfounded. If Botany discountenances this idea, 

 Chemistry would seem to scout it altogether ; for silk contains 11-33 per cent, of nitrogen, 

 and caoutchouc contains none at all, being simply a solid hydro-carbide, and therefore 

 widely dissimilar in constitution to silk, which consists of oxygen 34-04, nitrogen 11 '33, 

 carbon 50-69, and hydrogen 3-94, in 100 parts. 



This hydro-carbide emulsion is of common occurrence in the orders Eitphorbiacecs 

 and Urticacea, which may be looked on as the main sources of caoutchouc. The 

 American caoutchouc is said to be furnished by the Siphonia elastica, or the Hevea 

 Guianensis of Aublet, a tree which grows in Brazil, and also in Surinam. 



Dr. Eoyle sent models of cylinders of 1^ to 2^ inches in diameter, and 4 or 5 inches 

 in length, to both the Asiatic and Agricultural Societies of Bengal, to serve as patterns 

 for the natives to mould their caoutchouc by. Mr. Griffith says that this plan of 

 forming the caoutchouc into tumblers or bottles, as recommended by the committee 

 of the London Joint-Stock Caoutchouc Company, is, in his opinion, the worst that can 

 possibly be offered ; being tedious, laborious, causing the caoutchouc to be blackened 

 in the drying, and not obviating the viscidity of the juice when it is exposed to the 

 sun. He recommends, as a far better mode of treating the juice, to work it up with 

 the hands, to blanch it in water, and then subject it to pressure. Better methods 

 have recently occurred while experimenting upon the caoutchouc juice. This fluid, 

 with certain precautions, chiefly exclusion from air and much warmth, may be kept in 

 the state of a creamy emulsion for a very long time. Mr. Hancock states, some 

 barrels treated with ammonia arrived in England in a fluid state. 



However plausible these observations may appear, the practical men wanted sheet 

 rubber to cut into threads, &c., and Mr. Hancock states ho had a cylinder made of 

 masticated rubber, of a convenient size, and sent it to Para as a pattern for the natives, 

 and great numbers of cylinders were soon after in the market, well made, of the 

 quality desired, and called tubes. Such cylinders are still imported (1857). 



Great interest was taken by Mr. Hancock to introduce the native juice into this 

 country ; and, after great expense, he had the disappointment of finding the barrels 

 contained coagulated India-rubber and watery fluid. Some samples, by peculiar 

 treatment, escaped ; whatever might have been expected, there seemed but little 

 confidence in these plans, and valuable as the native juice might be at one time, yet 

 by solvents and by working the rubber with machinery, it is far more profitable 

 to employ this state, than to import a large quantity of watery fluid, with all the 

 expenses of casks and cooperage, while the solid article is excellently adapted to take 

 care of itself. 



