PRESERVATION OF TIMBER. Ill 



9f\^ iiitKicmceci bv imbibition a deliquescent salt, such as the muri- 

 ivi' )i li.Tiv.-, vvhicii retains moisture powerfully, as is well known, 

 a;i i 35ems to have U\<?. power of giving a remarkable degree of sup- 

 p!eii33s to wooJ. Tla^ experiments, contrived to show the elfects 

 of deliquescent silts, were made upon deal, which is allowed to be 

 one of the most brittle woods. After havino; impregnated it with 

 concentrated solutions ii was sawed into very thin veneers, some of 

 which I have seen in the possession of M. Bouchcrie, which after 

 being strongly twisted and bent in various senses, immediately re- 

 gained their original flatneso and evenness when they were left 

 free. 



Warping, or shrinking, is occasioned by alternate shrinking and 

 swelling in consequence of varying hygrometric states of the atmo- 

 sphere. When timber is worked before it is thoroughly seasoned, — 

 and this is apt to happen in regard to pieces of large scantling es- 

 pecially — the shrinking is of course extremely conspicuous when the 

 time necessary to complete desiccation has elapsed. It is this in- 

 convenience which makes it imperative on builders of all kinds, ship- 

 builders more especially, to keep stocks which necessarily absorb 

 a considerable amount of capital. It has lonjj been a question with 

 engineers to find a remedy for this state of things. Seasoning, in- 

 deed, is now effected somewliat more quickly by squaring the logs 

 at the time the trees are cut down ; but the loss of time is still very 

 considerable. The mode of seasoning by the stove or vapor has 

 been abandoned as too costly. 



After having found that the shrinking and separation of pieces of 

 carpentry did not begin to take place until the timber was upon the 

 point of losing the last third of the moisture which it contained at 

 the time of being cut, M. Boucherie thought that to prevent all 

 warping and shrinking it would be enough to retain this quantity of 

 water in combination with the woody tissue ; in other words, to pre- 

 vent complete desiccation. Facts have proved the correctness of 

 this view. Pieces of wood kept at a certain unchanging degree of 

 moistness by means of a deliquescent salt infused into their pores, 

 do not change their bulk or form, in spite of extreme variations in 

 the hygrometric state of the air. Such pieces of wood, however, 

 exhibit great differences in point of weight under the influence of 

 different circumstances. 



Several planks of great breadth and extremely thin were prepared 

 with chloride of lime and joined together; some of them were left 

 unpainted, others were painted on one side, or on both sides ; after 

 the lapse of a year these planks were found not to have shrunk or 

 warped, while similar planks of the same thickness and kind of 

 wood, but unprepared, were found to have cast in an extraordinary 

 way.* 



M. Boucherie has done more than this ; he has not only had it in 

 view to preserve wood and to prevent it from warping, qualities so 

 desirable, — he has made use of the same faculty of imbibition to im- 



* Boucherie, op. cit. p. 151. 



