iu:l ANTISKI'TK; TKHAIMENI- OF TI.MP.Ki;. 



(HO' ('.), in order to render them more durable. It is found tliat if 

 the immersion is continued for a longer period, the wood becomes 

 brittle, and that chloride of zinc, blue vitriol or creosote poisons the 

 wood and renders it dangerous to the miners. — Tr.] 



4. Sititabilitff of different Wood for Injection. 



The question as to the comparative ease or difficulty with 

 which a jiiece of wood can be injected and whether the injection 

 is thorough, or merely superficial, cannot as yet be satisfactorily 

 answered. As a rule, a thorough injection is rare, in most 

 cases the antiseptic liquid merely injects the sapwood and 

 younger woody zones ; in the case of railway-sleepers which 

 are injected pneumatically, it also passes into the two ends of the 

 sleepers, whilst the heartwood in the centre is often only partially 

 injected. There are, however, many modifications in the above 

 condition of injected wood, according to the species of wood, its 

 soundness or unsoundness, special anatomical structure and 

 amount of contained resin, which differs greatly in individual 

 cases. 



According to species, woods without heartwood, or with 

 imperfect heartwood, are much more easily injected than those 

 with heartwood. 



It has been proved by experience, that the beech is the wood 

 most easily injected and that hornbeam, aspen, birch and alder 

 come next, then spruce and silver-fir. As regards heart- 

 wooded trees, although the sapwood may be readily injected, it is 

 an exception when the heartwood can be injected at all and then 

 only partially. Different woods also absorb antiseptic liquids in 

 difterent degrees; thus on the Kaiser Ferdinand Railway, 50 cubic 

 feet each of oakwood and Scotch pinewood absorbed respectively 

 240 lbs. and 570 lbs. of antiseptic substance. In fact the more 

 porous a wood the more easily it is injected. 



[Houlton states that up to GOOlbs. of heavy tar-oil may Ijc absorbed 

 by a load of timber. — Tu.] 



The degree of soundness of the wood is also influential in this 

 respect, as only sound wood-fibres are capable of injection. 

 Young wood being generally sounder than old wood is more 

 absorbent than the latter. 



