THE PARA RUBBER TREE 126 



The preparation of the forms (1) to (4) and the methods 

 employed in drying and smoking the rubber have been 

 ah-eady described in the general part of this book (see 

 pp. 74-7) and need not be repeated here. 



Scrap rubber consists of the shreds which coagulate in 

 the incisions or in the collecting-cups and other utensils. 

 It is exported in tlie form of balls or cakes, or it is con- 

 verted into crepe by passing it through a washing machine 

 and is then sometimes made into block. 



A small quantity of rubber may be recovered from the 

 shavmgs of bark removed dm'ing tapping by macerating 

 them in water and then passing the mass through the 

 washing machine until the vegetable tissue is eliminated. 



Considerable interest is being taken by planters at 

 the present time in the adaptation for plantation use of 

 the Brazilian method of preparing Para rubber by smok- 

 ing the latex (see p. 105). Several machines, notably 

 those designed by Wickham and Derry, have been intro- 

 duced for carrying out the process on a commercial scale, 

 and trials with these are now being made. It is, however, 

 too early to say whether the rubber prepared in this way 

 will be preferred by manufacturers to the present forms 

 or whether the process will prove suitable for general 

 adoption on rubber estates. 



Yield of Rubber from Cultivated Para Trees. — The yield 

 of rubber fm-nished by individual Para trees varies con- 

 siderably with the conditions under which they are grown, 

 and it is now generally considered that the yield per acre, 

 which is more constant, affords a more satisfactory basis 

 for calculating returns than the average yield per tree. 



In Malaya dming 1911 the average yield of rubber from 

 the whole area tapped was about 200 lb. per acre, and it 

 must be remembered that many of the trees were being 

 tapped for the first time. It is estimated that the return 

 from five- to six-year-old trees in Malaya may be safely 

 put at about 250 lb. per acre, whilst the yield from older 

 trees is correspondingly higher. 



The average number of trees per acre in Malaya is about 

 150, so that a yield of 250 lb. of rubber per acre would be 

 equal to about 1| lb. per tree. In this connection the 

 following figures, which show the average yield of rubber 

 per tree in Malaya during 1906, 1907, and 1908, may be 

 quoted : 



