stood, that it was the inspifsated juice of a tree, a native of Guiana and other provinces on the eastern coasts of South America, which was there known under the name of Hevea, and which was recognised by Linnæus to be a species of the Iatropha; nor was it, for many years, suspected that a substance possessing similar qualities could be obtained from any other plant. Some specimens, however, of substances approaching in qualities to the American Coutchouc, though differing from it in some particulars, having been accidentally found in various other parts of the globe, excited a suspicion that there might be many other plants that afford juices pofsefsing qualities of the same sort, which has caused experiments to be made that clearly evince the certainty of this fact. There is a kind of Coutchouc that comes from China, which is not, in all probability, the produce of the Hevea. I have myself seen a kind of Coutchouc that was brought by a ship-master from the coast of Guinea, which he himself made from the juice of a tree in that country that he could not scientifically describe; and which, though much resembling the Coutchouc of America, appeared to me not to be entirely the Some specimens of this I believe I can still obtain, should any gentleman who has skill and leisure for experiments wish to have them for that purpose; and of the benefits that may be derived from such experiments I shall soon have occasion to adduce some powerful illustrations. It is now also well known, that many plants of the torrid zone afford a juice which, when inspifsated, approaches to the nature of Coutchouc in several respects; among which may be

same.

ranked the Ficus religiosus et indica, the artocarpus integrifolia, Hippomane biglandulosa, Cecropea peltata, &c.; there are even some plants of European produce which possefs a similar quality, particularly the chondrilla juncea, Linn. a native of the south of France; the milky juice of the common fig-tree, that of several kinds of the Tythemales and Apocynium, the white misletoe (viscum album. Linn.) are said to possess many of the properties of the Coutchouc; and Mr. Faujas de St. Fond gives a preparation of the viscid juice obtained from the common holly, which, for some purposes, may be substituted for the Coutchouc.

But none of the substances that have yet been discovered so nearly resembles the original Indian rubber of America in its most valuable qualities, as that which forms the subject of the present memoir. It was accidentally observed in the island of Pulo-pinang, off the coast of Malacca, adhering to the wounded parts of a rambling plant that grows there to an immense height, supporting itself upon trees, and running from one to another for many hundred yards in length; so that it was not without some difficulty that the parts of fructification could be obtained, so as to ascertain its botanical characters. It is also found in the island of Sumatra, whence Dr. Roxburgh (to whom the world is indebted for innumerable botanical discoveries in India) obtained perfect specimens by the care of Dr. Charles Campbell of Fort Marlburgh, so as to be enabled perfectly to identify the plant, by ascertaining its botanical characters.

The juice which affords this concrete is, like all the others that afford any thing of a similar quality, of a

Howison (who first communicated to the Asiatic society an account of the tree that yielded it, under the name of the Elastic gum vine), as so much resembling animal milk in its most obvious appearances, that it might be easily mistaken for it by a careless observer. "The best juice," says he, "is always produced from the oldest vines. From them it is often obtained in a consistence equal to thick cream, which will yield two thirds of its own weight in gum.

"The chemical properties of this vegetable milk, so far as I have had an opportunity of examining them, surprisingly resemble those of animal milk, From its decomposition, in consequence of spontaneous fermentation, or by the addition of acids [Qu. did he try the animal acid of the stomach of creatures living upon milk,-rennet?] a separation took place between its caseous and serous parts, both of which are very similar to those produced by the same procefses from animal milk. An oily or butyraceous matter is also one of its component parts, which appears upon the surface of the gum as soon as the latter has attained its solid form. The presence of this considerably impeded the progrefs of my experiments, as will be seen hereafter.

"I was at some trouble in endeavouring to form an extract of this milk so as to approach to the consistence of new butter, by which I hoped to retard its fermentative stage, without depriving it of its useful qualities; but, as I had no apparatus for distilling, the surface of the milk that was exposed to the air instantly formed a solid coat, by which the evaporation was in a great degree prevented. I, however, learned, by collecting the thickened milk from the inside of the

70 The Coutchouc of Pullo-pinang and Sumatra. coats, and depositing it in a jelly pot, that if excluded from the air, it might be preserved in this state for a considerable length of time.

"I have kept it in bottles, without any preparation, tolerably good, upwards of one year; for, notwithstanding the fermentation soon takes place, the decomposition in consequence is only partial, and what remains fluid still retains its original properties, although considerably diminished.”

Mr. Howison then proceeds to detail the manner in which he made gloves, boots, and various other articles of this substance, by first making molds of wax of the proper size and shape, and then covering them with the juice. He found that the immersing the mold in the milk and then exposing it to the air did not at all answer upon trial; "that fluid running almost entirely off, although none of the oily matter was present." Neither did he find that a brush answered well for laying it upon the mold; for the moment a brush was wet with that fluid, the hair became united as one mafs. In short, he found no mode answer so well as that of dipping the fingers in the fluid, and then rubbing it with some degree of pressure all over the molds.

When so wetted, the molds, hung upon a peg over a vefsel placed for receiving the drippings, were usually so dry as to admit of receiving another coating in the space of ten minutes: however, "after every second coat, the oily matter before mentioned was in such a quantity upon the surface, that, until washed off with soap and water, I found it impofsible to apply any more milk with effect; for, if laid on, it kept running

He found that thirty coatings were required before it attained the usual thicknefs of the bottles that come from America.

He made in this way very neat gloves and boots, and for these uses it seems to be much superior to the American Coutchouc, on account of its pofsefsing none of that clamminefs when wetted that is observable in the other.

But, although he contrived to give his boots soles, heels, and straps by a very simple and easy procefs, yet he found that the boots in a short time lost their shape, and were subjected to other inconveniences, which he thinks would render them unfit for drefs where elegance is required; but for fishermen, and others who are necefsarily obliged to be long in water, they may prove useful, as they entirely prevent all accefs to that fluid.

Our ingenious experimenter having conceived an idea,, that if an elastic cloth, in some degree correspondent to the elasticity of the gum, were used, the defects abovementioned might be in a great measure remedied, he accordingly made his first experiment with Cossembazar stockings and gloves.

"Having drawn them," says he, " upon the wax molds, I plunged them into vefsels containing the milk, which the cloth greedily absorbed. When taken out they were so completely distended by the gum in solution, that, upon becoming dry by exposure to the air, not only every thread, but every fibre of the cotton had its own distinct envelope, and in consequence was equally capable of resisting the action of fluid bodies as if of solid gum.

"This mode of giving cloth as a basis I found to