Page:Popular Science Monthly Volume 50.djvu/702

682 investigations. Some confusion prevailing in regard to the expression "India rubber," what follows may justify the English name of the substance: In 1765 Aublet announced his discovery of the tree in French Guiana. In 1772 Magellan, descendant of the great navigator (Le Caǫutchouc et la Gutta-Percha, E. Chapel), proposed caoutchouc, or "résine élastique de Cayenne," as a substitute for bread crumb in erasing pencil marks. It was known in France as peau de négre. In England, where the discovery was attributed to the celebrated Priestley, who only propagated a foreign idea, designers soon came to call the article "Indian rubber." It was not known as a product of Asia until 1798. Hence the thought of the time probably connected it with its South American habitat and thus with its Indian gatherers. The appearance of the little cube in the shops about 1775 was the beginning of the great part now played by India rubber in the arts, sciences, and industry. In 1780 Berniard, a Frenchman, experimented in a line with Hérissant and Macquer, and found oil of turpentine to be the best solvent. He also succeeded in imparting various colors to the gum.

By 1791 syringes, sounds, bougies (1779), and elastic bands had been made of caoutchouc. The manufacture of impermeable tissues had been tried in France in 1791 by Besson. The idea was borrowed from the Indians, from whom the early Spaniards had learned to gum their hempen cloaks, which when thus treated were impervious to rain, but degenerated in the sun. Hancock and Mackintosh, in England, were the first to make waterproof garments, later than 1818, the rubber cloth being used as lining (E. Chapel). Hancock devised important processes for treating rubber, and in 1838 invented ink erasers; but it remained for Mackintosh alone, by employing benzene as a solvent, to produce, in 1823, the first successful garments, which at once came into great favor, in spite of their disagreeable odor. At present, three tissues are made: "simple tissues" (having one rubber face), "double-faced tissues" (rubber on both sides), and "double tissues" (two stuffs with one rubber coating between). "Mackintosh" is "double tissue," and the method of manufacturing it is substantially the same as at first, only machinery is used. In the calender machine the fabric is spread with rubber solution, is drawn by a roller under a scraper to remove excess, and passes upon a steam table, where the solvent evaporates, leaving a thin pellicle of rubber on the stuff, which thoroughly dries in passing around a drum and is wound upon a mandrel. It may then be taken to the front of the machine and the process repeated. Ten coats are sometimes applied. The product must afterward be vulcanized, to render it less sensitive to heat and cold.

Many do not understand how much we owe to vulcanization