68 



or WOOD m general 



Greenheart {Neddndra Rodiaii) commonly develops two crossing 

 heart-shakes for two or three feet up the butt-end of the log. 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 conversion of a 

 log into plank wellnigh impossible. 



It is this hindrance to the conversion of timber into plank that 

 constitutes the main practical importance of all forms of shake, 

 as they do not at first involve any decay, and consequently do 

 not much interfere with the employment of the logs in bulk. 

 Heart-shake, however, is probably in itself an indication of that 

 incipient decay that comes when timber has passed its maturity 

 and the older layers shrink more than the outer. 



Fig. 89.--Heart-shake. 



Rind-galL— Somewhat allied to cup-shake is the local defect 

 known a^ rind-gaU, This originates from the destruction of part 

 of the bark of a growing tree, whether by another tree falling 

 against it, the scorching of a forest-fire, the gnawing of an animal, 

 or even the cutting of initials by some misguided youth. If the 

 cut has penetrated to, exposed, and destroyed the cambium, there 

 may, in spite of the gradual overgrowth of layers of new wood 

 from the margins of the injury, be a local want of cohesion between 

 the exposed wood and that subsequently formed over it. This 

 defect may entirely escape detection from the outside of an un- 

 converted log. 



Decay.— Bright-looking wood is generally of better quality 

 than that which is dull; while any departure from the usual 

 colour of the timber of the species is commonly, as we have 



