510 AUXILIARY FOREST INDUSTRIES. 



and of these the following are at present in the front rank : 

 sulphate of copper, chlorides of zinc or mercury, heavy tar- 

 oils (creosote) and milk of lime. There are also a few other 

 substances the use of which is still only in the experimental 

 stage. 



Injection with sulphate of copper (blue vitriol) was employed 

 in France on a large scale first by Boucherie, and has been 

 used extensively since 1841 for building-timber, railway- 

 sleepers and telegraph-poles. Formerly this method was 

 used extensively by railway-companies in France, Austria, 

 and Bavaria ; this is no longer the case, though it is still 

 employed here and there for telegraph-poles, stakes and other 

 small pieces of timber exposed to decay. Wood injected with 

 sulphate of copper is harder than wood in its natural condition, 

 but is rendered more brittle and weaker by the process. 



[The salt also is washed out of the wood easily and it 

 reacts on all iron with which it may come in contact, so that 

 iron-fastenings applied to wood so treated must be galvanised, 

 or coated with zinc, and the wood tarred at the points of 

 contact. Tr.] 



Sir W. Burnett, in 1838, patented a process of injection by 

 means of chloride of zinc, which is at present used in many 

 German, Austrian and American railways. Chloride of zinc is 

 one of the cheapest antiseptic substances, and recent experience 

 has proved that it is preferable to sulphate of copper. 



[Chloride of zinc does not corrode iron but is said to be 

 washed out by water ; to prevent this the Wellhouse * process 

 has been invented in America. Glue is added to the solution, 

 which is forced into the timber, and subsequently a solution 

 of tannin is pumped into the injecting chamber, at a pressure 

 of 100 Ibs. to the square inch, forming with the glue a leathery 

 substance which fills the pores of the wood and prevents the 

 washing out of the zinc chloride. Tr.] 



The use of chloride of mercury (corrosive sublimate) was 

 patented in 1832 by the Englishman Kyan as a preservative 

 for timber. 



[Kyanising was for some time used extensively in Britain, 

 and is useful in dry situations but useless in sea-water ; 



* "Engineer," Sopt 11, IS'Jl. 



