28 



TIMBER AND TIMBER TREES. [CHAP. 



FIG. Sa. 



thirds the semi-diameter of the tree. This is of serious 

 consequence to the converter who has to deal with it, as 

 the defect completely separates the concentric layers 



into segments of cir- 

 cles. The simplest 

 form in which we find 

 this shake (Figs. 8 a 

 and ), is that of a 

 straight line crossing 

 the pith, and taking 

 a direction in the same 

 plane through the 

 length of the stem. 

 It will, however, be 

 found in some speci- 

 mens to have taken a 



twisting form, and on examining the top of the tree, the 

 shake may be nearly at right angles to that at the butt- 

 end (Fig. 9). This is 

 about the worst form, 

 as it would involve a. 

 most serious loss in 

 the conversion of the 

 log if it were an ob- 

 ject to reduce it into 

 plank, and often ne- 

 cessitates its being 

 employed in bulk. 



The twist in the 

 heart-shake just re- 

 ferred to is pro- 

 bably the result of an effort made by the tree to turn 

 upon its base, which, I should think, might happen to 

 trees produced in dense forests, where light and air are 



FIG. 



