RUBBER PLANTING 237 



in contact with a rotating wheel of definite composition 

 for a certain time and with a certain pressure, and the 

 loss in weight of the rubber is afterwards determined. 

 For stretching tests special machines are used in order 

 to cut perfect rings from sheet of uniform thickness. 

 The ring is tested by passing it round two rollers, which 

 rotate at an even speed whilst they are gradually moved 

 further and further apart by a stretching force, the 

 amount of which is recorded upon a dial. The force 

 required in order to produce a certain elongation, or to 

 break the ring, may thus be determined. 



CONCLUSION. 



We have now followed the fortunes of rubber from 

 the wild territories of the Amazon to the plantation, 

 and from the plantation to the factory. Here we may 

 take leave of it, conscious that the last word on the 

 subject is far from being said. In fact, we shall pro- 

 bably be safe in asserting that the future history of the 

 rubber industry will be at least as interesting and 

 eventful as its past history. At every stage of its 

 career, rubber still presents problems which the planter 

 and the manufacturer must join hands in solving, with 

 the help of their scientific advisers. 



