838 PRINCIPLES OF AMERICAN FORESTRY. 



ride of zinc and two-thirds of dead oil (creosote oil). Chlor- 

 ride of zinc was formerly used alone, but it was found that 

 it washed out after a few years, where the wood was laid 

 in contact with the ground, and thus the wood was liable 

 to decay ; but by the addition of dead oil, which is itself a 

 good antiseptic, the cells of the wood were effectually 

 sealed over and water prevented from entering, and thus the 

 chloride of zinc was protected and the process made more 

 permanent. The cost of this treatment in Hessen, Ger- 

 many, is estimated at about twenty-two cents per tie. In 

 this country Pine ties are recently reported to have been 

 impregnated in this way for 9 cents per tie. 



Among the other processes for the preservation of wood 

 are the following: 



Kyanizing Process. In this the ties are steeped in a 

 solution of bichloride of mercury (corrosive sublimate), 

 in the proportion of about one part bichloride to one hun- 

 dred parts, by weight, of water. The time required 

 for this process is about one whole day for each inch in 

 thickness. This material is an active poison, and must 

 be handled carefully. It has given excellent satisfaction 

 in the preservation of timber which comes in contact 

 with the soil, but soon corrodes metal in contact with it. 



Boucherie Process. In this process the timber is 

 impregnated with a one per cent, solution of sulphate of 

 copper, either by pressure in a closed vessel or by apply- 

 ing it to the end of the tie or log and forcing it through. 

 This is an excellent antiseptic, and is said to have doubled 

 the life of the Pine ties in Europe. 



Creosoting. This process is very extensively used, 

 and has given excellent satisfaction. The material is 

 what is known as dead oil, of coal tar, and is obtained by 

 distilling coal. Naphthalin is its principal preserva- 

 tive. A similar oil, known as wood creosote oil, is ob- 

 tained by the distillation of Pine wood, but is said to 



