mp:thods of injection. 663 



does not form chemical combinations with metals. On the 

 Emperor Ferdinand Railway, in Austria, a mixture of chloride 

 of zinc and carbolic acid is being used with good results. 



Blythe at Bordeaux injects wood with steam containing tar-oils. 



[Boulton considers that no good can result from this, the light 

 oils being too volatile to remain long in the timber ; on the other 

 hand, the injection of heavy oils in the form of vapour is prevented 

 by their high boiling point ranging from 400° to 760° F., while timber 

 is rendered brittle and unsafe for engineering purposes at a tempera- 

 ture of 250° F.— Tr.] 



Stuart Monteith first used milk of lime to fill the pores 

 of timber ; this method has been reintroduced by Frank and 

 is useful for preserving furniture and other woodwork under 

 cover, but its utility is doubtful for wood in the open. 



[An American, Haskin, has introduced a process termed vul- 

 canising, by which green wood in trucks is passed through an 

 iron cylinder 6^ feet in diameter and 112 feet long, where it is 

 subjected for a few hours to compressed air at temperatures of 300° 

 to 500° F.; this converts the sap of the wood into neutral oils, i-esins, 

 &c., which act as antiseptics. Haskin maintains that this high tem- 

 perature docs not weaken the wood. — Tr.] 



3. Methods of Injection. 



The method of injecting wood by the various substances 

 already referred to is as influential on the result as the antiseptic 

 substance itself. The most important methods are : — hydro- 

 static injection, pneumatic injection, imbibition by immersing or 

 boiling the wood in solutions of the antiseptic substances. 



(a) Hydrostatic injection. — At first the antiseptic liquids were 

 absorbed by natural force of the foliage raising the sap, incisions 

 being made with this object at the base of the stem of a standing 

 tree. This method was abandoned owing to its impracticability 

 [and the fact that the foliage exerts only an upward pressure 

 equivalent to that of 10 or 12 feet of water.* — Tr.]. Boucherie 

 discovered that a pressure of one or two atmospheres applied at 

 the transverse section of a log is sufficient to expel the sap and 

 replace it by another liquid. 



* Boppe op. cit. , p. 93. 



