2 9 8 THE RUBBER INDUSTRY 



lected during the day's work, and to compare the final 

 results with the output of estates where no attempt 

 at such distinction has been made. In the Amazon 

 Valley the latex is of much more even quality than in 

 the Orient ; in many extensive districts the variation in 

 density is barely perceptible ; the trees in tapping are 

 all of mature age, and the method of coagulating the 

 latex by immersing in the smoke of the Urucury nut is 

 a guarantee that no excessive absorption of carbonic 

 acid can take place. The difference in quality of rubber 

 from Para is due to the different varieties of the Hevea 

 Brasiliensis common to different sections of territory, and 

 not to any variation in methods of preparation. 



Another cause for variability in the plantation prod- 

 uct is the rolling and tearing of the rubber sponge 

 after coagulation ; in the case of the Brazilian product 

 no manipulation whatever takes place after the latex is 

 coagulated, and the excess of moisture saturated with 

 carbonic acid remains in the rubber and acts as a pre- 

 servative. 



Grading. No adequate system of grading plantation 

 rubber has yet been attempted. It is not sufficient to 

 separate the rubber into four or five classes, as is done 

 at the present time in the Orient; the finer qualities 

 should be subjected to classification by experts before 

 shipment, or by laboratory tests after arrival in London 

 or Liverpool, as suggested recently by the Rubber 

 Growers' Association. In the Amazon Valley the 

 grading is done by experts at the port of shipment, and 

 the effectiveness of this operation is proved by the 

 willingness of manufacturers to purchase large consign- 

 ments of Para rubber on the classification set out in 

 bills of lading. 



