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If a planter can by testing, assure himself that he is producing 
a break of rubber which will pass high when similarly tested by 
the .purchaser, he is less likely to be working in the dark when 
changing and improving his methods of preparation. 
This apparatus was designed as a ’simple and accurate machine 
to carry out a physical test of rubber so that the planter on the 
estate could satisfy himself as to the resilience and elasticity of 
his rubber before shipping it and also in the hope i that the buyer 
might find it useful to supplement his manual ancl other tests by 
using such a machine. 
The principal of the apparatus is, to Submit a piece of rubber 
of a standard size (obtained by cutting with a sharp knife with 
parallel blades) to a constantly increasing strain of known amount 
during a constant time and temperature. In order that this machine 
should be of use in brokers’ offices and on plantations as well as 
in scientific laboratories, it was made as simple as possible and 
quartz sand was chosen as the substance used for the weight in 
straining because it is less affected by temperature than mercury 
or water and is more easily cleaned than either of these. The 
sand used should pass through a No. 4 sieve, i.e. y having 40 meshes 
to the inch. 
The apparatus consists of a large copper case with a water 
jacket at the base so that the interior can be kept at a constant 
temperature. The case has a glass door in front so that readings 
may be taken without altering the temperature. 
A graduated glass cylinder containing quartz sand is so fixed 
that from the outside the sand may be made to flow into a receiver 
which is attached to the hanging pieze of rubber which is to be 
tested. Pointers running on a finely graduated scale can be moved 
from outside the apparatus to determine the original length of the 
rubber and the extension owing to the pull ^ by the strain of the 
inflowing sand. 
The process is as follows : — 
A piece of rubber of a given size a convenient size and shape 
is 15 centimetres (5-^- inches) long by 7 centimetres (2f inches) 
wide and 3 m. m. thick (abo.ut y^-th inch) is placed between the 
clamps. These clamps consist of two parallel rods one of which 
moves up and down and the rubber is folded over so as to clamp 
itself. I found that all screw clamps however accurate by the 
surfaces had been prepared did not hold the rubber equally and 
pulled slightly away at some point. 
After the rubber has been in the clamps for a few minutes, the 
pointers are adjusted and two horizontal marks made at a distance 
of 5 centimetres apart on the rubber, these lines are made with a 
fine Indian ink point. The hanging vessel is then put on to the 
lower clamp. The stop-cock at the bottom of the glass cylinder 
is then opened and an equal and constant flow of sand passes into 
the receiver which is attached to the lower clamp. The time 
taken for the sand to run through is about five minutes, but this 
