NOTES^. 
257 
closely to the above estimate. MM. Michelin state that the quality 
of the samples sent to them was at least equal to that of the very best 
corresponding commercial rubbers, but that an exact valuation could 
not be given, as the samples were too small. 
A comparison of Mr. Parkin’s samples with the samples obtained 
by the old method of tapping shows that the shell rubber of the latter 
is almost or quite as good as regards the yield of rubber from the 
sample. It is thus evident that the great advantage in all these 
processes is their cleanliness in collection of the milk ; comparison 
with the ball rubber of the old process shows the difference. There is 
no special virtue, as regards the percentage of rubber obtained, in one 
method rather than the other. In actual fact there is no great gain 
in using the acid if the climate be fairly dry, so that the natural 
coagulation and drying can take place quickly ; but the use of creosote 
as a preservative is perhaps always advisable. 
The acid or mercury coagulation method, however, seems to have 
some advantage when we go on to the third set of figures giving the 
detail of analysis. The greater the proportion of resin in rubber the 
less its value, and the acid-prepared samples seem to have less than 
the samples prepared by simple drying. MM. Michelin remark that 
the proportion of resin soluble in acetone in the Ceylon samples is 
closely similar to that in the corresponding native rubbers. They 
remark also that the proportion of resin soluble in acetone or in benzine 
and alcohol is no greater in rubbers altered by heat or light than in 
those not so altered ; the proportion is only increased when there is a 
chemical action or oxidation at the same time. Thus, sample 5, though 
sticky, contains less resin than samples 3, 8, and 9, which are far 
superior for commercial purposes. Caoutchoucs may be quite spoiled 
by the action of heat without increasing the proportion of resin. 
Another point of interest is the difference between the rubber of old 
trees and younger ones, e.g.^ as indicated in samples 2 and 4, in which 
trees of 12 and 22 years old respectively were employed. It would 
of course be absurd to lay much stress on these figures, but so far as 
they go they show that the rubber of the old trees is no better, if, 
indeed, it be not worse (as containing more resin) than that of the trees 
12 years old. 
From the planter’s point of view the chief lesson to be learnt from 
Mr. Parkin’s work and the above analyses is to practise the greatest 
possible cleanliness in collecting and preparing rubber ; any rubber 
dried on the tree or otherwise contaminated will sell for a much lower 
price as “ scrap ” or “ negro-head.” By Mr. Parkin’s method of 
collection in separate tins under each cut and placing water in the tins 
the great bulk of the milk can be brought in in the liquid condition and 
filtered, and can then be treated in clean tins, with or without acid, as 
local experience shows to be suitable. Quick drying is advantageous, 
but excessive heat must be avoided, as under its influence the rubbei' 
