THE WORK OF THE FOREST DEPARTMENT IN INDIA. 55, 



The methods by which timber can be treated may be divided: 

 into four classes, namely, (i) brush treatment, (ii) immersion in; 

 open tanks, (Hi) treatment in pressure cylinders and (iv) hydro- 

 static injection. The first is not an impregnation method but 

 relies on protecting the timber by applying a superficial layer 

 of paint or antiseptic oil. Immersion in open tanks is suitable 

 for treating posts, telegraph poles, mining props, and limited 

 quantities of sleepers or building material. Of timber arti- 

 ficially protected in Europe and America, the greater proportion, 

 is treated in pressure cylinders, while hydrostatic injection is 

 not now in common use. 



Many treating processes have been evolved, differing both 

 in the antiseptic used and in the method of introducing it into 

 the timber. The antiseptics which are at present employed may 

 be divided into two main groups, namely, oils and salts ; by far 

 the most important oil is coal-tar creosote. Many other anti- 

 septic oils have, from time to time, been put on the market, 

 either patents or otherwise, but nearly all of them are derived 

 from coal-tar creosote. The other oils to which attention has 

 been paid in recent years are petroleum products. 



A large number of salts have been employed in the treatment 

 of timber, of which chloride of zinc has best withstood the 

 test of time. Of other well known salts may be mentioned 

 copper sulphate, corrosive sublimate or bichloride of mercury, 

 saccharine and arsenic solutions and compounds of fluorine. 

 The various processes embodying the employment of these salts 

 have generally been named after the inventors of the processes, 

 such as burnettizing, employing chloride of zinc, the Boucherie 

 or Margary process, in which copper sulphate is used, and 

 powellizing, in which molasses and arsenic form the chief 

 ingredients. Besides the above processes may be mentioned the 

 Haskin or vulcanising process, in which the substances in the 

 timber are sterilized and rendered unfit for the nourishment of 

 insects and fungi. 



The primary factor governing the treatment of timber in 

 any country is the procurability of a good grade of cheap coal- 

 tar creosote. This oil is not at present available in India, all 

 supplies having to be imported. Again, the variable climate 

 in different parts of India not only affects the timber to be treat- 



