479 
vised than the ordinary carpenter's chisel, carefully used with a 
light mallet. The cuts (three oblique cuts one above another, 
should be clean cut, and should not penetrate into the wood of the 
tree. Caution should be exercised in this respect, as if the wood 
is injured certain species of boring beetles attack the tree. The 
spacing should be about a span apart, one circle round the trunk of 
the tree beginning at the ground surface for each day s tapping, 
and so giving an increased number of cups in use as the tree grows 
in circumference, with proportionate increase in yield of the latex. 
One advantage of the close system of cultivation recommended, 
besides greater economy in working is that centrally placed curing 
stations can be secured. This is necessary in order that the latex 
may be quickly treated, so soon as it is taken from the trees or 
much of it will become coagulated before it could be subjected to 
the smoke-curing process, and so lose the higher market value. 
The Hevea is naturally a large tree, under favourable conditions 
attaining a girth of 12 ft. in the bole. To stint it in matter of root 
space or scope will be found to be false economy. I would, there- 
fore, strongly deprecate closer planting than that recommended, viz. 
half chain (33 ft. by 33 ft/), 40 to the acre. Planted and cultivated 
at this distance and giving say, 5 rubber per tree at 3-y. only 
per pound, it would yield at the rate of some £30 per acre for sa e 
of rubber alone, apart from value of the seed crop, to be converted 
into oil worth £ 2 5 to ^30 per ton. 
The Contract Journal , January 8th , 1902. 
METHOD OF EXTRACTING RUBBER FROM 
THE BARK OF RUBBER VINES. 
A series of buildings for exploiting the bark of the wild rubber 
vines in Cochin China are being built. A factory containing 
machinery for treating 2 to 3 thousand kilogrammes of bark a day 
is in course of construction at Cho Quan (province of Choion). I he 
barks employed are those of Day-Che and Day Nam do trong. 
The method of treatment will consist in putting the dry bark of the 
vines to macerate for 4 or 5 days in sulphuric acid at 50 degiees, 
the cellulose is then destroyed and carbonized, when the ra bber 
remains unhurt by the acid, when taken out of the acid bath, tie 
bark is washed to free the rubber from the acid and especially to 
recover the acid, which is eventually obtained by evaporating the 
water in which it has been washed. The disintegrated bark is 
then put under the action of a separator which can be moved 
either -by hand power or machinery. It receives meanwhile 
currents of water alternately hot and cold and bv this action 
the bark already dissolved by the acid goes off in a state oi mud, 
the rubber separated collects in sheets about a centimetre in 
thickness. This operation is rapid enough and scarcely demands 
more than hand labour, since on 100 Kilogrammes of bark the acid 
required for the solution 100 Kilogrammes reduced it is since from 
50 to 45 degrees only entails a loss of 2 Kilogrammes. The rubber 
