110 PRESERVATION OF TIMBER. 



the tenth day it is almost entirely gone. In favorable circumstances 

 these ten days suffice to effect the complete impregnat4nn of the 

 largest stem. In one of his experiments upon a poplar, M. Boucherie 

 saw the absorbed liquid reach the height of about 95 feet in seven 

 days. 



In the white woods it is found that there is an axis of variable 

 diameter in different cases which escapes or rather which resists 

 impregnation. In hard woods the parts which are not penetrated 

 are the inner or undermost circles of the heart. M. Boucherie, after 

 having ascertained these facts, explains them thus : in the white 

 woods, according to the testimony of the workmen, the central part 

 which resists the penetration is at once the weakest and the most 

 perishable portion of the log ; there is no longer any circulation, any 

 life there ; it is dead wood interred in the midst of the living woody 

 layers. This absence of penetration of the woody tissue appears, 

 on some occasions, elsewhere than in the centre of the trunk and 

 branches ; it presents itself under the most various forms and in 

 different parts of the trunk : it appears to depend, as has been said, 

 on the presence of wood abstracted from the influence of vital phe- 

 nomena, and which, impenetrable itself, presents a barrier or an ob- 

 stacle to the passage of the solution to other parts ; it is thus that a 

 knot, or a piece of rotten wood, is generally found as the starting 

 point of the zones that have escaped imbibition. As to the non- 

 penetration of the most central parts of the heart of oak, elm, &c., 

 M. Boucherie views it as affording unquestionable proof of the fact 

 that there the living juices of the tree had long ceased to circulate. 



The distinction generally drawn between the white or soft, and 

 the perfect or hard wood, rests on the differences of color presented 

 by a transverse section of the trunk. In the oak, for example, the 

 external and nearly white concentric layers are held as the soft and 

 valueless portion of the log, and are commonly hewn away in squar- 

 ing it ; the darker, more central portions constitute the heart-wood, 

 the valuable timber. But, according to M. Boucherie, the distinc- 

 tion is different when the fact of penetrability is taken as the guide, 

 and all that portion of the trunk which imbibes is considered as 

 alburnum, or soft wood, and all that does not imbibe is regarded as 

 hard wood. The alburnum in this way is so much extended that it 

 may be found constituting three-fourths of the whole mass of the 

 trunk. Once introduced, the pyrolignite of iron, according to M. 

 Boucherie, is not only useful in preserving the wood, it also in- 

 creases the density of the timber. Impregnated with this salt of 

 iron, wood becomes so hard as powerfully to resist the tools of the 

 oarpenter and joiner, who even complain of the increased difficulty 

 with which it is worked. - 



Flexibility and elasticity in timber are qualities in request for cer- 

 tain purposes, particularly for ship-building. The fir timber of the 

 north of Europe is much more prized than that of the south, espe- 

 cially for masting, on account of its greater flexibility and elasticity, 

 qualities which appear to depend in a great measure en the quantity 

 of noisture retained ; to increase these qualities M. Boucherie has 



