326 



The resistance to heat at 80° all well preserved, the 5 year old 

 trees rather better than the others. Messrs. Michelin consider that 

 there is practically no difference between these samples. However 

 they were not large enough for exhaustive experiments. 



A third suggestion has been that the dfferences in soil and 

 climate between South America and Tropical Asia is the cause of the 

 difference between the two rubbers. M. Petit ^Encyclopedie Roret 

 Caoutchouc et Gutta Percha) compares the position of linseed, as 

 produced in Russia, India and the Argentine, the oil of which has 

 different properties and qualities in these different countries, and 

 suggests a parallel in rubbers. 



M. Gerber states that the rubbers of different regions of Amazo- 

 nas have different values and pu<-s it thus : there are "crus de 

 caoutchouc comme il y a des crus de vin" (i.e. — there are vintages of 

 rubber as there are vintages of wine). However, he says it is possible 

 and probable that these differences are due to various causes, local 

 methods of preparation, skill and care on the part of the operator, etc. 

 Besides the balls of rubber are marked with the name of the maker 

 and those that bear certain marks are the ones inost valued and 

 sought for. May not, says M. Vernet, each tree produce rubber 

 possessing its own individual properties.? This occurs in other trees 

 and probably also in Para Rubber, 



Another suggestion not made by M. Vernet, but which he will 

 doubtless refer to in the continuation of the series of articles is that 

 the rubber tree that we cultivate in Asia is a different strain or variety 

 from that now supplying the bulk of the Amazonas rubber. 



Practically all the Asiatic trees sprung from one lot of seed 

 collected at Tapajos, but nowadays the bulk of the South American 

 rubber comes from a much more remote district and it is certainly 

 probable that the tree would vary in different districts and its pro- 

 duce would equally vary. Specimens of the plants from the areas at 

 present worked have been received at Kevv and they appear identical. 

 It does not follow, however, from this that the rubber would be 

 identical. An expert in rubber from Brazil visiting the Botanic 

 Gardens at once identified the tree and rubber as what was formerly 

 known as Tapajos, or low river rubber, and stated that it was not 

 considered as good as Bolivian. 



With respect to the analysis showing that rubber from young 

 trees is not richer in resins than that from old trees, and to the state- 

 ments sometimes made that for commercial purposes young is as 

 good as old, if the preparation is equally good, one would receive this 

 with caution in view of the great difference in strength and pull of 

 the two. Evidently much more chemical research is wanted in the 

 matter. — Ed. 



