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local conditions. However, it is with the protection of building-s 

 and the preservation of woodwork generally that we are here 

 generally concerned ; and a few points on the efficient and eco- 

 nomical treatment of timber may be worth bringing forward. 

 The efficient preservation of woodwork is necessarily of more 

 pressing importance in Termite infested conntries than in the 

 temperate zones where timber is for the most part only subject 

 to the slower processes of bacteriological decay and not exposed 

 to the attacks of such voracious insects, the destructive powers 

 of which are startling in their rapidity. 



The basis of all processes of preservation is the impregnation 

 of the wood fibres with some antiseptic material toxic to living 

 organisms. The means to accomplish this end are various, but 

 may be broadly classified under three headings : ( 1 ) The pres- 

 sure or combined vacuum and pressure method; (2) the open 

 tank method; (3) the brush method. 



For the practical planter the first method is out of the ques- 

 tion on the point of the cost of the special plant necessary for 

 transportation of the timber to some large centre where such 

 a plant may exist. 



The open tank, or immersion method, however, calls for some 

 detailed consideration, as the only equipment absolutely neces- 

 sary is any available watertight receptacle of sufficient length to 

 take the timbers to be treated. Where time is no object the 

 immersion of the timber in a cold preservative solution for a 

 period of anything up to three or four days will ensure sufficient 

 impregnation. Given, however, facilites for heating the solution, 

 the treatment with any preservative can be greatly accelerated. 

 Where such facilities exist, however, the quickest and most ef- 

 fective results can be obtained by immersing the timber, heating 

 the solution up, and maintaining it at a temperature of 180° F. 

 to 200° F. for half the total time for which the timber is to be 

 immersed. The solution should then be allowed to cool for the 

 remainder of the time before the timber is to be removed. The 

 underlying princii)le of this operation is that the preliminary 

 heating of the solution has the effect of expelling the air from 

 the timber and ex])anding the wood cells. As the cooling pro- 

 ceeds a partial vacuum is produced, so that the preservative so- 

 lution fills the cellular spaces from which the air has been dis- 

 placed. The manufacturers of the well-known Atlas '*A" Wood 

 Preservative have carried out tests witli railway sleepers, from 

 which it has been determined that timber immersed for twelve 

 hours in a solution heated for six hours and allowed to cool for 

 the remainder of the time will absorb a greater percentage by 

 weight of the preservative than similar timber immersed for 

 twenty-four hoiu's heated continuously for the whole period. 



lender no circumstances can such thorough impregnation be 

 obtained by the brush method as by immersion : but in many 

 instances where sundrv small (|uantities of timber have to be 



