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Saps and Exudations. 



are selected both by natural and by artificial selection. The condition in South 

 America is, I understand, one of jungle in which the trees affect, and compete with, 

 one another, and this leads to the survival, by natural selection, of the finest and 

 most sturdy only of the seedlings. The native in tapping selects the best of the trees 

 he conveniently can, and here the influence at work is one leading to the rejection of 

 weak and badly developed trees. On the plantation after the first selection of the 

 stumps and seedlings, no further selective progress is actively at work. To deter- 

 mine whether this has any influence on the quality of the rubber, tapping should be 

 done on specially selected trees, and the quality of the rubber extracted compared 

 with the average rubber of that plot of trees. All opinions at present must be looked 

 upon as guesses at the solution of this question, the only thing certain is that plant- 

 ation rubber is inferior, and this certain knowledge is one of the most important 

 results of my visit to England. I propose to endeavour to find out in Singapore, and 

 on the plantations themselves, the actual reasons of this inferiority by experimental 

 work ; and to this end I have had made in Manchester, by a firm of manufacturers of 

 rubber machinery, at the expense of the Colonial Government, machines for practi- 

 cally working up and vulcanising rubber, and I intend with the aid of these machines 

 to manufacture test pieces of vulcanised rubber from raw rubber taken from trees 

 grown in various localities of different age and cured in different ways. With these 

 samples of vulcanised rubber physical tests of elasticity and tensile strength will be 

 carried out, and a just comparison of the samples among themselves, and with true 

 South American Para can be made. There are special difficulties in carrying out 

 physical tests on india-rubber, and there is at present no uniform method of stating 

 results ; comparisons between tests made by different places are therefore of little 

 value, and it is essential that all the work be done in the same manner on the same 

 type of apparatus, to eliminate the personal equation and correctly ascribe to each 

 variant factor in the production of the raw rubber its consequent variation in the 

 quality of the product. When this is done I shall be able to say with certainty 

 which method of preparation gives the best results, and to ascribe correctly to each 

 and every one of the variable conditions under which the rubber is produced its true 

 influence on the quality of the rubber. This work I look upon as being important, 

 and it will, I trust, settle decisively many of the problems which now are controver- 

 sial. To see clearly the necessity for the work, and to have gained the insight into 

 the methods of treating and vulcanising rubber necessary for carrying it out, are the 

 direct results of my visit to England, and the time spent in the works of the rubber 

 manufacturers there. 



(To be continued.) 



A NEW ERA IN RUBBER EXTRACTION. 



There has been developed, principally in connection with the Mexican shrub 

 known as " G nay ale," a very considerable interest in the extraction of commercial 

 rubber from plants not adapted to any method of tapping. Many processes have 

 been utilized, all based in part upon the maceration of the plant as a whole, and 

 the ultimate separation from the mass of all the rubber contained. 



As is well known, very much of the world's present supply of rubber is 

 obtained by methods other than the tapping of the trees. A vast amount of 

 rubber— including the South American grades marketed as " Caucho," or Peruvian 

 —has always been collected by felling the trees and "ringing" trunks at frequent 

 intervals, to allow the latex to escape. Gutta-percha and Balata are obtained in 

 the same way. The Landolphia climbers in Africa are torn down from the forest 

 trees, and cut into small pieces, from each end of which the latex exudes. Some 

 millions of pounds more of rubber are gained in Africa from plants which contain 

 the material only in the roots, the bark of which is beaten off with stones, the 

 gummy mass resulting being boiled by the natives to separate the rubber. 



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