ACCIDENTS DURING GROWTH 155 



to the wood formed prior to the injury. Such a 

 defect is not easily detected in standing timber, 

 but when cut the wood below the site of the 

 injury peels away in flakes. 



Shakes, of which there are three kinds, are 

 all too common defects in timber. A shake 

 in plain terms is a split or cleft in the timber ; 

 it may be a heart shake, star shake or ring shake. 

 Of these, the most frequently met with is the 

 heart shake. A heart shake is a spUt which 

 passes right across the centre of the stem and 

 is wider at the middle point than at its extremi- 

 ties. Shakes of this nature may occur in prac- 

 tically all trees. Laslett, in his Timbers and 

 Timber Trees, states that certain kinds of 

 Northern Pine, Pitch Pine, Greenheart, True 

 Teak and Tooart are especially hable to heart 

 shakes. Whilst other Northern Pines, Canadian 

 Red Pine, Elm, African Oak, Spanish Mahogany 

 and Sabicu are little hable to this defect. As 

 Boulger states, " One of the worst forms of this 

 defect is when, owing to spiral growth, the 

 shake shifts its direction as we trace it up the 

 stem. It may in this way sometimes be nearly 

 at right angles at one end of the tree to its 

 direction at the other, thus rendering the con- 

 version of a log into plank weUnigh impossible. 



It is this hindrance to the conversion of 

 timber into plank that constitutes the main 



