404 FOREST PRODUCTS 



temperatures. Commercial rubber hardens at the freezing point (32 F.) 

 and temporarily loses its elasticity but, on the other hand, it does not 

 become brittle. 



The center of the American rubber industry is at Akron, Ohio, to 

 which many large automobile tire concerns have gravitated within the 

 past decade. 



Had it not been for the development of a successful method of arti- 

 ficially growing rubber trees, particularly in the Far East, rubber would 

 be exceedingly expensive on account of the tremendous demands for it. 

 Methods have been developed for the manufacture of rubber by syn- 

 thetic processes, but no methods have been evolved to manufacture it on 

 a basis to replace the natural rubber. Great strides have been made in 

 the past decade, not only in the amount of imports of rubber to this 

 country, but in the manufacture of the crude form, as well as in the han- 

 dling of rubber plantations, the tapping of the trees and the reduction of 

 the milky fluid or latex into the crude rubber state. 



SOURCES OF SUPPLY AND METHODS OF PRODUCTION 



Up to 1914 the principal source of india rubber was Brazil, where the 

 province of Para was the center of production. The so-called Para 

 rubber is the standard by which all rubbers have been judged. Since 

 that year, the principal source of supply has been the plantations of the 

 Malaya and the surrounding sections of the Far East and for the past 

 five years the production of plantation rubber has had a most remarkable 

 development. 



Wild rubber is also produced in nearly all sections of the tropics. 

 Aside from the regions mentioned above, considerable quantities of 

 rubber are produced from a variety of plants in Central America, Africa, 

 Mexico, the northern countries of South America and the West Indies. 



The following species are the principal sources of rubber supply, 

 in the approximate order of commercial importance: 



i. Para rubber occupies the pre-eminent position in the world's 

 rubber markets. It is derived from several species of Hevea, principally 

 Hevea braziliensis (Mull, Arg.) which, in both the wild and planted 

 forms, supplies about 80 per cent of the world's rubber production. 

 There are extensive forests in the valley of the Amazon River, especially 

 in the province of Para, but it also extends along the tributaries of this 

 river to Peru, Bolivia, Venezuela and the Guianas. The rubber area in 

 Brazil alone is said to cover 1,000,000 square miles. The Para rubber 



