444 THE POPULAR SCIENCE MONTHLY 



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 dis- 

 covery in 177.0 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 stand- 

 ing 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 rub- 

 ber industry received an impetus when pneumatic tires came into use for 

 bicycles, and the employment of rubber as an insulator in electric instal- 

 lations also increased the demand, but the dominating factor in the con- 

 sumption 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 fig- 

 ures. Import of crude rubber into Great Britain was in 



1830 23 tons 



1850 381 " 



1870 7,656 " 



1910 43,848 " 



The rubber plant grown in houses for ornamental purposes is usually 

 Ficus clastica, 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, Euphorbiaeeae, belongs Manihot Glaziovii also found in a 

 small section of Brazil. It produces the Ceara rubber of commerce. 



