•Part TV.] R. S. Pearson: Antiseptic Treatment of Timber. 115 
absorbs the antiseptic solution more readily than the latter, resulting in 
varying depths of impregnation in the timber. This should be avoided, 
as far as possible, as it may result in an unnecessary amount of the oil 
or salt entering into one portion of the sleeper and an insufficient 
saturation of other portions of the fibre. To overcome this difficulty, 
the United Provinces Authorities divide their sleepers into two classes, 
namely, (i) those containing ^rd or more of sap-wood and (ii) those 
■containing less than U’d of sap-wood, each class being treated 
separately. 
The other factor governing the absorption of an antiseptic is the 
percentage of moisture in the timber : this point has already been dealt 
with under “ Seasoning of Timber.” In this connection it is interesting 
to note that green timber absorbs the solution much more slowly than 
-does seasoned timber, while the maximum capacity of absorption of 
quite green wood is barely half that of seasoned timber. 
(ii) The amount of antiseptic necessary to preserve the 
TIMBER. 
The quantity of an antiseptic with which it is necessary to impregnate 
timber, will depend on the use for which the timber is intended. Thus, 
piles destined for marine work, or telegraph poles to be placed in marshy 
ground should be treated “ to refusal ” which, in the case of conifer 
timber, containing much sap-wood, may amount to 15 lbs. to 20 lbs. 
per cubic foot. The amount of creosote required for sleeper treatment 
will vary from 5 lbs. to 10 lbs. per cubic foot, according to the class of 
timber dealt -with. For instance, the Finns longifolia sleepers, which 
are being treated by the United Provinces Forest Department, are being 
given 5 lbs. per cubic foot, this being considered enough to protect the 
sleepers sufficiently long to ensure their being rejected for mechanical 
defects before the fibre is destroyed by fungus or white ants. On the 
other hand,, when dealing with the Dipterocarp sleepers, the timber of 
which is much superior to that of Finns longifolia , 7 lbs. to 8 lbs. per 
cubic foot is advocated; while Terrninalia tomentosa, which is again 
superior for sleeper purposes to the Dipterocarp timber, should be 
treated to refusal. 
To obtain the above results, Open Tanks can generally be used if 
the amount of absorption does not exceed 4 lbs. or 5 lbs. per cubic foot, 
and the number of sleepers to be treated does not exceed 30,000 to 50,000; 
but, for heavier impregnation or where larger numbers of sleepers are 
involved, Pressure plants should be employed. 
[ 245 ] k 2 
