56 



TIMBER AND TIMBER TREES. 



[chap. 



FIG. 9. 



most serious loss in the conversion of the log if it were 

 an object to reduce it into plank, and often necessitates 

 its being employed in bulk. 



The twist in the 

 heart-shake just re- 

 ferred to looks like the 

 result of an effort made 

 by the tree to turn upon 

 its base, and it has been 

 supposed that it might 

 happen to trees pro- 

 duced in dense forests, 

 where light and air are 

 very scant, or perhaps 

 to trees unequally ba- 

 lanced in their branches, if grown in the open. There 

 is more evidence, however, of its being due to the 



twisting in the spiral 

 turns of grain noticed in 

 many trees, and which 

 is connected with the 

 interpectination of the 

 fibrous and other ele- 

 ments during the 

 growth of the wood.* 

 The heart-shakes are 

 equally disadvanta- 

 ^'°- '°- geous, if, indeed, they 



are not more so, when 

 they cross each other at the pith, and open to the full 

 diameter of the tree, splitting it into four segments. 



* This spiral growth is common in the Turkey Box tree ; it is also fre- 

 quently seen in the Fir and Pine species, and occasionally in other woods, e.g. 

 Chestnut. 



