28 TIMBER AND TIMBER TREES. [CHAP. 
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 6), 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 
RN the conversion of the 
log if it were an ob- 
ject to reduce it into 
Wt 1 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 
Fic, 84, 
