India Rubber. An elastic, gummy substance, consisting of the coagulated milky juice of various trees and shrubs found in Central and South America and Africa. This juice is contained chiefly in the middle layer of the bark, in a network of tubes, and in its natural state is of a pale yellow color of the thickness of cream. The natives tap the trees of mornings and during the day half a pint of the fluid is received in a clay cup placed at the trunk. This at once begins to harden, which is hastened by exposure to the smoke and heat of a fire. The Amazon valley, generally known as North Brazil, comprises an area almost as extensive as that part of the United States east of the Rocky mountains. It is probably the richest valley in natural and agricultural resources on the globe, extending on a line with the equator almost 2 000 miles due westward to the base of the Andes in Peru and Bolivia. Practically nothing is produced in this valley, because the gathering of rubber is more profitable than anything else. Everything necessary to sustain civilized life is imported, principally from Europe. Two-thirds of the rubber exported goes to the United States. The natives sell it for about twelve cents a pound to the merchants of Para, but its value on reaching this county is about 50 cents a pound; though the top grades often fetch as high as 95 cents a pound. The rubber forests of Brazil will ultimately be exhausted, owing to the reckless mode followed by the tappers. The ordinary product of a tapper's work is from 10 to 16 pounds daily. There are merchantable in New York between 30 and 40 sorts and grades of India rubber, the variations determining the selection by manufacturers in the purchase of stocks. Of course rubber in all its variations is essentially the same, differing somewhat in the same degree as a pumpkin in Dakota differs from that in New England -one large and the other small, one with little flavor and the other rich in food qualities. The difference between sorts of rubber, however, is due in large measure to the methods employed in gathering the sap. It happens that the natives of the Amazon valley have always taken pains in the curing of rubber. While climatic conditions in that country may have had some influence upon the quality of "Para," the condition in which this rubber is exported has become a prime factor in making it a favorite with the manufacturers. On the other hand, some of the African sorts are so full of bark and stones as to make them almost unfit for use. At one time the African rubber was almost unmarketable in New York, the price sinking as low as 10 cents per pound, and not wanted at that. One factory, after long experimenting, discovered a chemical solution in which the rubber was washed, the process being that the bark and other impurities absorbed the chemicals making them so heavy that they separated from the gum and fell to the bottom and away. This company made a fortune in a moderate space of time, but the price of African rubber gradually went up, from the fact of their creating a demand for it until the profits became comparatively small, when they disposed of the privilege of washing to some leading rubber factories, who use the process at the present day.

As the raw India rubber is unloaded on the piers at New York it is in the form of balls, or shapeless lumps, and in this condition it is received by the rubber factories. At the factory these lumps are first placed in a vat of boiling water and softened, next sent to the masticating machine, where it is ground up very fine and mixed with sulphur. After being several times passed through this machine, which is built on the principal of a "sausage grinder," the rubber is worked through heavy smooth rollers under an enormous pressure, which packs it together in the form of a sheet or mat, about the size and thickness of cow-hide. This sheet is then thoroughly dried, which requires from 4 to 6 weeks. Next it is passed through a series of very hot rollers, until it is sufficiently pliable to admit of being spread upon cotton cloth. This operation is performed between two iron cylinders, the pliable rubber being run in over one and the cloth over the other, the heavy weight forcing it thoroughly into the meshes of the cloth. In this manner, rubber, or rubber cloth, of any desired thickness can be produced by simply regulating the distance between the iron cylinder from a thin gassamer tissue to a heavy boot sole. About 70 per cent of pure rubber is contained in the manufactured article. There are 120 india-rubber factories in the United States, employing 15,000 operators, who produce 280,000 tons of goods, valued at $260,000,000 per annum. This includes twenty rubber boot and shoe factories, each with a capacity of about 25,000 pairs of rubbers per day, whose products are shipped to almost every country in the world.

The remarkable substance known as india-rubber is composed of carbon and hydrogen alone, but its exact chemical nature is not by any means known with certainty. It was long used for various minor purposes before its valuable commercial qualities were appreciated. The French in 1751, first gave the matter particular attention, and in 1767 England issued a patent for making waterproof clothing; in 1825 a merchant of Boston introduced the original Para overshoe in its rough state, as made by the natives of the province of Para, Brazil, S. A. It was in this year that the wonderful capacities of the strange product began to be known, and the commercial world realized the fact that a new force had entered the industrial field, which was destined to play an important part in the arts and manufactures of the nineteenth century. To Charles Goodyear is due the credit of having devoted much time and money in experiments and improvements in the manufacture of rubber goods, and although he reaped no pecuniary reward from his patents, and though the French and English stole outright his invention of the vulcanizing process, their courts manifesting the greatest partiality and dishonesty in deciding against him, yet all countries and all consumers are indebted to Chas. Goodyear for bringing the manufacture of rubber to its present state of perfection. [See Rubbers, Mackintosh]