Page:Popular Science Monthly Volume 50.djvu/704

684 method of treatment have been made since Goodyear, who died in 1860.

The problem of regenerating vulcanized waste (old shoes, etc.) has not yet been satisfactorily solved, no means having been found to remove the sulphur completely, and to restore to the gum its original properties; yet there is an increasing tendency to use partly reclaimed rubber and foreign mixtures. From 1881 to 1883 the waste followed the rise in the price of the gum, and this led to the use of imitations made from linseed oil (first announced about 1846), from arachis, and from colza oil, and they still continue to be considerably employed in the fabrication of cheap articles.

Pure India rubber is whitish. It is rarely used, the vulcanized being preferred. Crude rubber is often mixed with pieces of bark, stone, clay, etc. The lumps are softened in hot water, cut into slices, generally by hand, and passed through washing rollers to remove foreign substances. When dried, they are ready for mixing with sulphur, etc., or for the "masticating machine," which kneads the stuff into a solid mass. The machine gets very hot and has to be cooled with water. The gum is then heated, molded, and cut into sheets by a rapidly moving knife. Balls, etc., which are made of these sheets, have to be cemented. It was not until about 1850 that manufacturers of "balloons" (hollow articles) began to make the endless variety of playthings with which the child of the present is familiar. India rubber grinding stones are made of the waste by an admixture of glass, pumice stone, or emery. Kamptulicon, of English origin, invented about 1843, is a mixture of rubber and pulverized cork applied to coarse cloth and covered with several layers of linseed oil. It is now largely superseded by linoleum (Walton's patent, 1860). Imitation leather and ivory (the latter not with complete success), hevenoide (for billiard balls, piano keys, etc.), baleinite, plastite (for gun rammers, canes, whip handles, etc.), and similar products are also made; even sponges. Stamps were made early in the history of India rubber, and by an American, James Peck, in 1862. They were ruined by the ink, and had to be abandoned until inks with an aniline base came, when they were able to supplant almost all their rivals. Hard-rubber dental plates are said to have been the invention of Dr. Evans, an American dentist in Paris, in 1854. He made several pieces for Goodyear's use in 1855. The latter showed them to Dr. Putnam in this country, who, with the assistance of a chemist and Goodyear, finally succeeded in making an article which has now obtained a high degree of perfection. Street-paving has been tried with success in London and Hanover. It deadens the rolling of vehicles, but the cost bids fair to prevent its general introduction. India-rubber horseshoes, an