Page:Popular Science Monthly Volume 85.djvu/448

444 to be more vigorous than it has ever been in the past. The difficulty of discovering a good solvent baffled chemists for a time, but in 1761 Herissant and Macquer used oil of turpentine and said that ether might also be employed. The name rubber seems to date from Priestley's discovery in 1770 of its power to erase pencil marks, the name caoutchouc being apparently a modification of the Indian name cahucha. In Priestley's time rubber could not be considered a plentiful article of commerce, its price being twenty shillings an ounce.

Though patents for the use of rubber as waterproofing had been taken out as early as 1791, Macintosh in 1823 seems to have been the first to make the industry a commercial success and the firm then started in Glasgow and afterwards removed to Manchester remains to this day as one of the most important in the rubber industry.

The next important step was taken by Hancock in England and Goodyear in America about 1840, the date being a little inexact because the process seems to have been in use before being patented. This was the addition of sulphur to rubber by which it is made capable of standing the hottest summer temperature without becoming sticky or losing its elasticity.

It was not till about 1886 that a process was discovered for depriving rubber of the smell which restricted its use for waterproofing. The rubber industry received an impetus when pneumatic tires came into use for bicycles, and the employment of rubber as an insulator in electric installations also increased the demand, but the dominating factor in the consumption of rubber has of late years been the automobile business. The very sudden demand in 1910 caused a tremendous rise in prices, and whereas during a portion of 1909 the price in London was 2s. 9d. in 1910 it reached 12s. 6d.

The growth of the rubber industry is indicated by the following figures. Import of crude rubber into Great Britain was in

The rubber plant grown in houses for ornamental purposes is usually Ficus elastica, which is native mainly to southern Asia. This is not the plant chiefly used for the production of rubber. Four different orders of plants provide commercial rubber and there are eleven genera belonging to these given in Thorpe's "Dictionary of Applied Chemistry." By far the most important is Hevea brasiliensis which provides the "fine Para" rubber of South America the standard of rubber in the trade. To the same order, Euphorbiaceae, belongs Manihot Glaziovii also found in a small section of Brazil. It produces the Ceara rubber of commerce.