HYGBOSCOPICITY. 



deviating from the vertical direction, is usually defective, so 

 that the best planks and other scantling are obtained by 

 rejecting the central plank and cutting the log into two or four 

 balks (Figs. 85 and 36), which can each be sawn up into suit- 

 able pieces. This obviously requires logs of somewhat large 



Fig. :;:i. (After Boppe.) 



Fig. 32. (After Hoppe. ) 



diameter, but yields timber that is much superior in quality to 

 that produced when smaller logs are merely sawn tli rough in 

 one direction. Dulianiel showed that by thus cutting a log into 

 four pieces, danger from cracks and warping is much diminished. 

 In Fig. 34 it is seen that the shrinkage of the four planks into 

 which the wood is thus divided 

 is quite uniform, and chiefly at 

 their outer ends. 



In India, where boxwood is 

 cut into round pieces for export, 

 each piece is sawn down to the 



:. :?l. (After 



centre along a radius, and this 



prevents any other cracks, the 



large opening widening or narrowing according to the degree 



of moisture of the air. This is also the practice in Japan 



(Fig. 37). 



In younger trees (Fig. 37) the concentric zones are fairly 

 uniform from the pith to the bark, while in older trees the 

 larger zones are shown in the middle of the transverse 

 section (Fig. 38). Hence the former usually crack in one 

 place, down to the radius, while in older logs there are 

 several internal cracks. 



When, as in railway-sleepers, a fairly thick plank is cut 



