Indian Forest Records. 
24 
[VOL. HI. 
pressure, his idea being that this would take place in unseasoned timber 
provided it was subjected to such pressure. 
The process is therefore to subject the timber to dry heat and high 
pressure, so as to coagulate the albuminous substances in the wood and 
change their chemical composition, thus to hermetically close each cell 
and at the same time render them unsuitable nutriment for fungi and 
insects, and by pressure to lignify the tissue. 
Necessary Plant required. 
So as to effectually bring about these chemical and mechanical 
changes it is necessary that the timber be in a green state when treated. 
The plant consists of one or more large iron cylinders of considerable 
strength sufficient to withstand the pressure necessary to lignify the 
timber. These are fitted with strong air-tight doors and running into 
them is a system of tram lines on which move the loaded trollies. 
A powerful air-compressing engine is required, as also an air-circulating 
engine, connected to the cylinders. 
Process of Vulcanizing. 
After the cylinders have been charged, a jet of steam is turned on to 
expel any surface moisture from the timber, which on collecting at the 
bottom of the retorts is drawn off by means of cocks. The air-compress¬ 
ing engine is employed to compress the air to a pressure of 200 lbs. 
per square inch, the heat generated by pressure being reduced by a spray 
of cold water. The moist compressed air is then dried and heated to 
between 94°C. and 149°C. and forced through the cylinders by the air- 
circulating engine. The hot dry compressed air is not allowed to stay in 
the Vulcanizing chambers but is made to circulate by allowing it to 
scape at one end in the same quantity as is forced in at the other, any 
drop in the pressure being compensated by the compression pumps. The 
process lasts from 6 to 10 hours according to the size of the timber to be 
treated. 
Cost of Plant and Treatment. 
Tne Secretary of the Haskin Wood Vulcanizing Co., Ltd., writing to 
the Consulting Engineer of Railways, Madras, states that the cost of an 
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