TIMBER AND TIMBER TREES. 



great extent, it is obvious that it will seriously affect the 

 cutting up of the timber into plankSj etc. 



The principal cause of "Heart-shake " is the unequal 

 loss of water, and consequent shrinkage, of the older 

 (central) parts of the wood, owing to the incipient 

 decomposition of that part and its consequent inability 

 to retain its usual proportion of water in antagonism to 

 the more powerful outer and younger parts. 



Another form of radial fissure has to be carefully 

 distinguished from the above. In this case the cracks 

 are wider and wider as we trace them outwards — i.e. 

 towards the bark. , Many of these so-called " Star- 

 shakes " are due to the more rapid drying of the ex- 

 ternal layers of wood, as the tree lies exposed on the 

 ground, after felling ; but there are other defects, also 

 expressed by radiating fissures which look very similar 

 to the last, to the inexperienced eye, but which are due 

 to quite other causes, often operating while the tree is 

 standing in the forest. The chief causes of these are 

 violent changes of temperature, but their peculiarities in 

 detail may be passed over here. 



Finally, the practised eye of the expert will search 

 for fissures which run in the planes of the annual rings, 

 and therefore cause separation, more or less complete, 

 of the layers. These " Cup-shakes " may be due to 

 violent and sudden changes of temperature, or to the 

 excessive bending of the tree before high winds, or to 

 other shocks— ^.^. the heavy fall of the tree or the log. 



Nor does this by any means exhaust the list of 

 possible defects in the wood, and to which the merchant 

 will direct his keen attention. He will want to know 

 whether the " grain "—i.e. the lines and planes of structure 

 —runs straight in the log, or whether it is twisted, as is 

 often the case in some woods. Then he will investi"-ate 



