Part IV.] R. S. Pearson: Antiseptic Treatment of Timber. 105* 
cent, of moisture. In Central India, the Punjab and Ra]putana 3 where 
temperatures run high and the moisture in the air is very low during the 
dry season, the percentage of moisture in timber falls below 10 per cent. 
It is therefore impossible to lay down a hard and fast rule as to what 
should be considered to be “ air-dry timber.” Provisionally, it may be' 
laid down that sleepers destined to be placed in dry, hot localities should 
not be treated if containing more than 15 per cent, of moisture and in 
wet localities not more than 25 per cent, of moisture. 
By accepting the principle that timber must be seasoned to a point 
commensurate with the degree of moisture and heat to which it will be- 
subjected after treatment, the question of how best to season the timber- 
must be considered. In the dry zone areas of India, there is generally 
no difficulty whatsoever in reducing the moisture in timber below 15 
per cent.; on the other hand, the process of seasoning is often so rapid 
that serious cracks develop in the timber, and it is only by protecting the 
timber from the direct rays of the sun that such defects can be reduced 
to a minimum. It is in the damper localities, such as the West Coast, 
parts of Bengal and Burma, in Assam, and in the Andamans that special 
measures may have to be taken to reduce the percentage of moisture 
in the timber and to hasten the process of seasoning. Natural seasoning 
in such localities will hardly reduce the moisture in the timber to 25' 
per cent., except perhaps for a short period during the hot weather. 
The prevailing conditions, therefore, point to the necessity for artificial 
seasoning of the timber. This is generally a somewhat costly process, 
and one which requires a certain amount of skill. Many patent plants 
exist which have been designed for seasoning timber such as, for instance, 
the Sturtevant or Erith’s processes. It is thought that to season sleeper 
weeds entirely in such plants would not be practicable, as the amount 
of timber to be handled would be very considerable, though it may be 
found profitable to use such plants to finish off the seasoning process, 
after natural seasoning has reduced the moisture in the sleeper as far 
as is possible. 
(c) Steam , Vacuum and Oil seasoning experiments. 
In Europe and America, and especially in the latter continent, timber 
is sometimes seasoned either with the help of steam and vacuum or by 
boiling in oil. To ascertain to what degree of dryness certain Assam 
species of timber could be seasoned by these methods, the writer carried 
out experiments in February 1916, at Digboi, in the same treating cylin¬ 
der as was used the previous year for treating the sleepers. Details of. 
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