This important gum is known by a variety of names. Caoutchouc, gum-elastic, and India-rubber. It is a product of the syringe tree of South America. This substance was first brought to Europe in 1735, by some French astronomers, who were sent to Brazil to make astronomical observations. It is found abundantly in Peru, Brazil, and Quito, and has recently been discovered in Asia. Considerable quantities of it are now obtained in Java, Penang, Singapore and Assam. In some places hundreds of miles are covered with trees. They are very lofty, rising to the height of fifty or sixty feet, without branches, but covered with a rich tufted foliage. The bark is exceedingly smooth, its leaves deep green, thick and glossy, and six or seven inches in length. The fruit consists of white almonds and is regarded by the natives as very delicious. The process of obtaining the liquid is very simple. A longitudinal gash is cut in the bark of the tree with a hatchet, a wedge is then inserted to keep the aperture open; the gum then oozes out in the form of a milky juice. A small clay cup is attached to the tree into which the sap flows. In the space of four or five hours the milk ceases to run, and the quantity received is about five table spoonsful. The cups are now emptied and the process of smoking is commenced; this with the forming process must be done as soon as the milk coagulates. A fire is built upon the ground made of the nuts of the wassou palm tree; over this fire an inverted earthen pot, with a hole in the bottom is placed, from whence issues a jet of pungent smoke. The smoke changes the color of the gum very slightly at first, but by exposure to the atmosphere it becomes first brown, then quite black, presenting the appearance which we see it has in articles of commerce. The sap of the tree is laid on a mould in successive layers, which are allowed to dry, and are formed into bottles and cakes, in which form it is exported. The natives of South America are very ingenious in the uses to which they apply it. Boots, shoes, syringes, and tubes, are among the many articles of domestic use into which it is converted. The tubes they use as torches, which burn very clearly, and emit but little odor. According to the celebrated chemist, Faraday, its composition is carbon, 87.2, hydrogen, 12.8—a hydro-carbon. It melts when exposed to a heat of 248°, and is resolved into vapor at 600°, and can be condensed into a liquid called caoutchoucin. In 1770, a cubic inch of India-rubber was sold in London for seventy-five cents, to erase pencil marks. It was not used to make water-proof fabrics until about the year 1800. These were first invented by Charles Mackintosh, of Glasgow, who applied a naptha solution to the surface of two pieces of cloth, then laid them together, passed them between rollers and thus cemented them together.
NATIVES GATHERING GUTTA-PERCHA.
A “Mackintosh” was the name applied for many years to a water-proof coat. Dr. Ure, although well aware of Mr. Mackintosh’s invention, coldly passes it over in his dictionary. It is supposed that personal feeling was the cause of this, as Dr. Thomson and Ure were once rival chemists in Glasgow, and Mackintosh was the friend and pupil of the former. The fabrics of Mackintosh had a most disagreeable smell, still he was the first person who established India-rubber manufactures in Britain, and perhaps the world. He afterwards removed his factory to Manchester, England. Various kinds of goods made of India-rubber soon afterwards began to be manufactured in England, but they were all decidedly objectionable to use, until the grand discovery of sulphurization was made; for this the world is indebted to an American inventor, Nathaniel Hayward of Woburn, Mass.
This substance, or rather, compounds of it, is now manufactured into so many articles of beauty and usefulness, that it forms an object of no small wonder to witness the rapidity with which such manufactures have sprung into existence.
The following description of the India-Rubber tree and its fruit is given by Chevalier D. Claussen, inventor of the flax cotton. He says that in the course of his travels in South America, he had occasion to notice the different trees which produce the India-rubber, and of which the Hancornia speciosa is one. It grows on the high plateaux of South America, between the tenth and twentieth degrees of latitude south, at a height of from three to five thousand feet above the level of the sea. It is of the family of the Sapotacæ, the same to which belongs the tree which produces gutta-percha. It bears a fruit, in form, not unlike a bergamot pear, and full of a milky juice, which is liquid India-rubber. To be eatable, the fruit must be kept two or three weeks after being gathered, in which time all the India-rubber disappears, or is converted into sugar, and is then in taste one of the most delicious fruits known, and regarded by the Brazilians (who call it Mangava) as superior to all other fruits of their country. The change of India-rubber into sugar, led him to suppose that gutta-percha, India-rubber, and similar compounds contained starch. He therefore tried to mix it with resinous or oily substances, in combination with tannin, and succeeded in making compounds which can be mixed in all proportions with gutta-percha or India-rubber without altering their characters. By the foregoing it will be understood that a great number of compounds of the gutta-percha and India-rubber class may be formed by mixing starch, gluten, or flour with tannin and resinous or oily substances. By mixing some of these compounds with gutta-percha or India-rubber, he can so increase its hardness that it will be like horn, and may be used as shields to protect the soldiers from the effect of the Minie balls, and some of these compounds in combination with iron, may be useful in floating batteries and many other purposes, such as covering the electric telegraph wires, imitation of wood, ship-building, &c.
A description of the various uses to which India-rubber is applied, will be found exceedingly interesting and instructive. The English have thus far succeeded more perfectly, or rather more generally in their application of it, than we, although since 1856, rapid strides have been made in perfecting the manufacture of the various fabrics in which it is used in our country, especially New England. It must not be forgotten that to an American is due the discovery of the process of sulphurization, which discovery immediately gave a new value, and a new impulse to the application of this wonderful product of the forests of South America.
The following account of the various uses to which India-rubber is applied, is taken principally from English sources, and refers to the manufactures of that country.
INDIA-RUBBER CLEANING PROCESSES.
The India-rubber, or caoutchouc, now imported to the enormous extent of six or seven hundred thousand pounds annually, reaches this country in masses of varied shape, but mostly of a dark color. In its imported state it is used for very few purposes; considerable modifications being necessary for its adaptation to practical service. It requires to be transformed into cakes, or sheets, or tissues, or tubes, or solutions, preparatory to its ultimate use; and this transformation requires operations of a somewhat peculiar kind, owing to the necessity of rendering the whole mass homogeneous in substance.