.•56 THE "WORK OF THE FOREST DEPARTMENT IN INDIA. 



ed but limits the number of antiseptics which it is possible to 

 use. For instance, the excessive heat experienced in the plains 

 makes the use of a high boiling point oil imperative, while the 

 -excessive moisture during the monsoon months precludes the 

 use of soluble salts. 



Some seven years ago it was decided to carry out a series of 

 •experiments by treating Indian timbers in connection with the 

 supply of sleepers to the Indian State Railways, the experiments 

 I)eing carried out by the Forest Economist, Mr. Pearson. The 

 object of the enquiry was two-fold, first to ascertain the best 

 and cheapest method of treating certain timbers and second to 

 prove to the railway engineers that certain of the less durable 

 timbers, after treatment, would meet their requirements. The 

 chief difficulty in deciding on what lines the enquiry should be 

 carried out was due to the fact that the cost of the most 

 universally used antiseptic, namely, coal-tar creosote, was ex- 

 cessive in India, while the cheaper salts if used alone were liable 

 to be washed out of the timber. With the object of keeping the 

 cost of treatment within practical limits it was decided to give 

 a trial to the Powell process, to undertake the treatment of 

 timber with small quantities of avenarius carbolineum oil, with 

 chloride of zinc followed by a thin protective covering layer of 

 a good grade of creosote, and lastly with a mixture of high boil- 

 ing point coal-tar creosote and cheap petroleum oil. 



The scheme further contemplated treating 1,000 sleepers 

 of each of five species, viz., Pinus longifolia, Pinus eaoelsa, 

 Terminalia tomentosa, Dipterocarpus alatus and Dipterocarpus 

 tuberculatus, with the four antiseptics mentioned, and handing 

 -over these treated sleepers to the State Railways to be kept 

 under observation. The work of treating these sleepers by four 

 different methods extended over four years; the first sleepers 

 to be laid down were those treated in 1911 by the Powell process, 

 while the rest were treated with the other three antiseptics and 

 laid down in successive years. All these sleepers were treated 

 in open tanks. More recently sleepers of the five species men- 

 tioned, together with several other kinds of timber, were 

 •creosoted in pressure cylinders either in India or in England, 

 some by the open cell or Riiping process, others according to 



