17 3 
and how in general it behaves in the vulcanising process as com- 
pared with Castilloa rubber in its present day crude and impure 
form, J have not been able yet to ascertain. This work is, however, 
in progress, and in due course I will report the results obtained. 
The amount of resin in Castilloa rubber shown above is absolute- 
ly unobjectionable, and does not in the least affect the quality of 
the rubber. I am quite aware that now and then all sorts of sinister 
actions are ascribed to the presence of resins in india-rubber, but 
« there is not the least particle of evidence to show that they are 
I intrinsically detrimental. As a matter of fact, in the manufacture 
of quite a number of rubber goods resins are deliberately added to 
the mixings. 
It is highly interesting to observe that the amount of resin in- 
creases in the trees from the root upwards, as the following tabic 
will show : — 
RESINS IN RUBBER DRAWN FROM 
Per cent. 
Trunk - - - 261 
Largest branches - - 3- 7 7 
Medium - - 4-88 
Young „ - - 5-86 
Leaves „ - - 7-50 
A similar increase is observed the younger the trees from which 
the rubber is drawn : — 
RESINS IN RUBBER FROM TREES. 
Per cent. 
2 years old - - 42-33 
3 " 35 02 
4 “ - 26-47 
5 - - 1 8*18 
o " ■ - 1 1 '59 
° >> ~ J‘2I 
It will therefore be seen that my advice not to tap the trees un- 
til ^ey are at least 8 years old is not only justified in the interest 
of the life and development of the trees, but also in the amount of 
resin which may safely be admitted in rubber of high quality. 
Riere are very few such observations on the amount of resin in 
rubber trees at different periods of their life, and in different parts 
or the tree, but it can scarcely be doubted that other kinds of rub- 
ber trees will, exhibit similar conditions, although the amount of 
lesin accompanying the rubber in different trees appears to varv 
not inconsiderable. But they never are entirely absent, and I am in- 
chned to think that the usual view of them as oxidation products of 
the india-rubber is altogether erroneous. 
Purity.— A s far as can at the present moment be seen, the fact 
is amply demonstrated that it is possible to prepare from the latex 
a rivtf 1 °n fF aSt u a a r ? bber Wh . ich for P urit Y is absolutely without 
a rival, and the physical properties of which place it at least on the 
level with the finest «r»de S of Para rubber" And this result is 
obtainable in working upon the milk of a tree, which so far has 
only been conspicuous for yielding the worst of all American rub. 
