Part II.] Pearson: Antiseptic treatment of Timber. 
41 
Adaptability of Indian Species to Treatment by the 
Open Tank Method. 
The most important question is the probable effect of the Open Tank 
treatment on our harder Indian timbers. Many experiments have been 
carried out in this connection on a laboratory scale and others are to be 
made on a large scale by treating several thousands of sleepers of the 
harder Indian timbers with different antiseptics. In the laboratory tests 
carried out no difficulty was found in treating the soft timbers as they 
readily take up the solution in which they are immersed. The case of 
moderately hard woods which are of sufficient strength for the purpose 
of sleepers is more difficult. By prolonging the period of immersion they 
can be made to take up sufficient quantities of the antiseptic to protect 
the timber, but the difficulty lies in fixing the period, as over-cooking 
means excessive cost of treatment, and on the other hand, curtailing the 
period of immersion may result in insufficient protection. Only extensive 
experiments with each species will settle this point. As regards the very 
hard woods, it is as yet doubtful if treatment by this method is possible. 
The results of laboratory experiments on such species as Sal, Padauk and 
Dhaura or Bakli (Anogeissus l at if olio) show that after immersion 
for 24 hours the solution has hardly penetrated one-sixteenth of an inch, 
probably an insufficient depth for their preservation ; on the other hand, 
many of the very hard woods are sufficiently good timbers to require no 
treatment, or are so hard that the cost of conversion of the timber into 
sleepers is impracticable. 
The Purpose for which the Treated Timber is required. 
The last point on which general remarks are necessary, before 
dealing in detail with the various antiseptics, is the purpose for which 
the treated timber is required and the climatic conditions of the locality 
in which it is to be placed. Our primary consideration is with railway 
sleepers and to a less degree with such timbers as are used for telegraph 
poles and fencing posts, mining-props and in construction work. The 
timber required for sleepers amongst other qualities, should be strong 
and hard, a condition not altogether favourable for treatment by the 
Open Tank method, but one that can probably be overcome by careful 
manipulation. The case of telegraph poles and fencing posts, as 
also that of mining-props is different, strength is essential but 
( H4 )' 
