114 
Indian Forest Records. 
[Vol. VI 
be necessary were it not first treated with the salt. This method of 
treatment is solely carried out with the object of reducing the cost and 
it is in no way claimed for it that it will render the timber more durable 
than would be the case were it subjected to a more drastic creosote treat- 
ment. 
(6) Cost of Treatment- 
The cost of treating a sleeper with an oil or salt will depend on (a) 
the power of absorption of the timber, (b) the amount of antiseptic neces¬ 
sary to protect the timber for a desired period and (c) the cost of the 
antiseptic, handling charges and plant. 
(i) Absorption. 
The degree of penetration of an antispetic depends on the method 
o treatment, the density of the timber, the arrangement and size of the 
pores, the percentage of sap-wood to heart-wood, and the percentage of 
moisture m the timber. Thus greater absorption can generally be 
obtained m Pressure plants than in Open Tanks , though the period of 
immersion is a more important factor than pressure. For instance, better 
penetration is produced by a long period of immersion at a relatively 
low pressure tnan by a short immersion period at high pressure. A^ain 
penetration does not take place laterally to the same "extent as it does 
a ong the fibre In conifer woods, the border pits allow of some lateral 
penetration taking place, especially from the distributing centres formed 
by dry resm ducts ; m no case, however, do the medullary rays allow of 
lateral penetration. Large pores are of great use in distributing the 
an.iseptic, a condition that makes it possible to treat dense hard-woods 
such as Termmalia tomentosa. In the case of straight-grained timbers 
con arning large wood-vessels, such as occur in Dipterocarpus pilcsus 
and D tuherculatus, treatment presents no difficulties, due to the 
i nward flow of the antiseptic down the large pores. Finns longijolia 
timber is equally easy to treat, not on account of the pores, which 
are absent but to the presence of large resin ducts in the timber. 
Spruce and Silver Fw on the other hand, are refractory to treatment, 
uue to the absence of distributing channels. 
Another important factor which governs the amount of absorption 
is the percentage of sap-wood to heart-wood in any given sleeper. Not 
infrequently, sleepers contain some of both, and the former, if dry, 
[ 244 1 
