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 b), 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 
