Page:Popular Science Monthly Volume 50.djvu/705

Rh American patent, are announced, for special use on asphalt pavements.

It is impossible to mention all the uses to which India rubber is applied, and reference can only be made, in concluding, to two more, very important ones. It is at present finding increasing favor in tires for vehicles, the solid kind being most frequent, though occasionally pneumatic-tired equipages are seen. Hancock claims to have made the solid kind for her Majesty in 1846. The recent tire of American invention with wires running through it is thought, in this country, to be the best, as double the quantity of rubber of better quality is used, which secures greater elasticity, and vastly cheaper, from better rim-construction and because worn spots may be cut out and renewed. The bicycle industry, it is estimated, is turning out, in 1896, in the United States alone, six hundred thousand bicycles and one million and a half pairs of pneumatic tires, which will require about one thousand tons of rubber. The output in England is about the same, that country and the United States producing seventy-five per cent of the wheels manufactured. A writer on this subject (Hawthorne Hill) recently said that probably not more than four per cent of the output of rubber is used in the bicycle trade.

The discovery of gutta-percha, which seems to unite all the advantages of India rubber, excepting elasticity, without its disadvantages, has sometimes been attributed to the traveler Tradescant, who brought it to England, where it was known as mazerwood. It was neglected and soon forgotten. To an Englishman, Dr. Montgomery, is due the merit of having brought the importance of the new article to the attention of the world of science and industry. Hearing of it at Singapore, in 1822, he procured specimens from the natives, who collected it in the neighboring forests, and formed it chiefly into axe handles by malaxation in boiling water. He found it differed materially from elastic gum. Having proved that it retained the shape on cooling, imparted to it in boiling water, while recovering its hardness and primitive tenacity. Dr. Montgomery thought such a substance could serve better than rubber for certain instruments of surgery, and communicated his views to the Medical Board of Calcutta in 1843, which warmly indorsed the idea. Ho also sent specimens and a study of the product to the London Society of Arts, and received from it a gold medal in recognition of his important discovery. According to Dr. Gützlaff, the celebrated missionary, gutta-percha was known in China long before it appeared in Europe, though certainly not gathered there.

Gutta-percha, like India rubber, is obtained from the juices of certain trees and climbers. The best is produced by a tree, the