198 TRANSACTIONS OF ROYAL SCOTTISH AREORICULTURAL SOCIETY. 



superior to that obtained by a superficial application of these sub- 

 stances. It may indeed be said that they act so long only as 

 the outer coating of creosote lasts ; for, from the time that this 

 has disappeared, through the action of the waves, or some other 

 form of friction, the Teredo bores into the wood in spite of the 

 creosote which it still contains. And similar results are observed 

 when arsenic, copper, or other substances are injected." ^ 



In fact, says M. Henry, it is very probable that if the 

 preservative substance has not penetrated deeply, its efficacy 

 will cease under superficial wear; but timber should be used 

 of species which admit of thorough impregnation,- and the 

 antiseptics should have sufficient fluidity. It has been 

 estimated that creosote injected to the extent of 300 kilo- 

 grammes to the cubic metre ' aff"ords absolute protection. 



From an American official circular on " The Preservation of 

 Piling against Marine Borers," it is learnt that' in America, 

 many methods of protecting piles from Teredo have been tried, 

 and that the following conclusions have been drawn : — A very 

 small exposed surface enables these marine borers to penetrate 

 a pile and to completely destroy it. To act eff"ectively, all 

 coverings must be absolutely continuous, and the antiseptics 

 must penetrate all the elements of the woody tissue. But all 

 such measures of protection are costly, and it is essential that 

 they should prolong the life of the pile sufficiently to make it 

 worth while to employ them. A comparison of the results 

 obtained by protective outer coverings and by injected anti- 

 septics shows that, properly applied, the latter are much more 

 efficacious than the former. The injected substance ought to 

 be insoluble in salt water, and it should penetrate deeply into 

 the wood. " If well carried out, this treatment yields a solid 

 antiseptic magma, into which the borers will not penetrate, and 

 the cost of the process is well covered by the result." Where 

 failure has occurred, this is attributable either to the use of oil 

 which was of inferior quality, adulterated, or insufficient in 



' Presumably M. Cligny is speaking of timber such as larch and Scots 

 pine in the round, with a penetrable zone of sapwood. — F.B. 



- In correspondence, however, M. Henry says that, for practical purposes, if 

 a pile is surrounded by a wide and well impregnated zone, it is not necessary 

 that the oil should penetrate to the centre. — F. B. 



2 Equivalent to 19 lbs to the cubic foot, which seems a very high figure. 



—F.B. 



