106 PRESERV^ATION OF TLMBER. 



friction ; nor do they always remove the causes of internal decay 

 on the contrary, by preventing- more complete dryness, they some- 

 times even provoke or favor them, when applied to tender, that is, 

 imperfectly seasoned wood. Merely laid on the surface, indeed, it 

 his always been seen that varnishes of any kind were but indifferen* 

 protectors ; that a really good preserver ought to penetrate the sub- 

 stance of ti..v3 wood, and unite with the tissue itself. But herein lay 

 the whole difficulty ; how was the needful penetration to be effected 1 

 for the number of chemical substances, from which good effects 

 might reasonably be anticipated, is pretty considerable, — unless in- 

 deed we find ourselves prevented from using them by the considera- 

 tion of the price ; for it is imperative that any preservative proposed 

 be extremely cheap. 



For a long time the only process for effecting the penetration of 

 timber by substances proposed for its preservation was to macerate 

 them for a longer or shorter time in a solution of the substance. 

 But this means was found as tardy of accomplishment as it was or- 

 dinarily imperfectly effected ; to have got to the heart of logs of 

 large scantling, years would have been required. Any delay, how- 

 ever, in such circumstances, is of itself a cause of enhanced price 

 of the article. By and by a variety of processes, the element in one 

 being pressure, in another exhaustion, were put in practice, and very 

 satisfactory results obtained. M. Breant showed, that by means of 

 strong pressure he could fill the largest logs from one end to the 

 other with any unctuous or resinous substance proposed, in the course 

 of a few minutes. M. Moll, a learned German, proposed creosote 

 introduced in the state of vapor by forcing, as an effectual means of 

 preserving timber, which it probably would be found ; but the high 

 price of the antiseptic, were there no other objections, would neces- 

 sarily be an obstacle to its general employment. The same objection 

 applies to the bichloride of mercury, (Kyan's patent;) and arsenic is 

 inadvisable from its deleterious effects upon the animal economy. 

 Some workmen are said to have lost their lives in consequence of 

 working timber which had been impregnated with a solution of whit(» 

 oxide of arsenic. 



It had been observed that vessels engaged in the lime-trade lasted 

 long ; and then it was naturally thought that by impregnating the 

 wood to be used for ship-building with lime it would be rendered 

 more durable. But the result did not answer expectation ; the tim- 

 ber treated with lime did not even seem to last the usual time.* 



Such was the state of the question when Dr. Boucherie made a 

 highly important communication to the Royal Academy of Sciences 

 on the preservation of timber. f Some estimate of its nature may 

 be formed from the list of subjects discussed in this remarkable 

 paper. 



1. To protect timber against dry-rot and the ordinary wet-rot 



2. To increase its hardness and strength. 



3. To ppjserve its flexibility and elasticity. 



• Dupin, Ann. de Chlmle, t. xvil. p.28S 

 t Idem, t. Ixxiv. p. 113. 



