IV.] 



STAR-SHAKE. 



57 



This form of the defect is very conspicuous in the Green- 

 heart timber (Fig. lo). 



The next important defect is the star-shake (Fig. 

 ii). This is found in many varieties of timber, and 

 occurs in trees of all ages and conditions of growth. It 

 consists of clefts radiating from the centre, or pith, which 

 often extend far towards — and even in bad cases touch 

 — the circumference of the tree, rendering it almost 

 valueless for conversion into board and small scantlings. 



The clefts or lines forming the star are generally 

 only slightly open, and 

 can scarcely be seen in 

 a fresh-cut tree, there 

 being no obvious signs 

 of decay about them. 

 They are, however, very 

 plainly perceptible 

 when the wood is mo- 

 derately seasoned, by 

 the matter forming the 

 two sides of the shake 

 having become some- 

 what darker in colour and more horny in texture by 

 exposure to the air. 



The principal cause of all such defects as those 

 referred to, and to that condition of the central parts of 

 many old treeSj especially Beeches, known as bois rouge 

 in France, is a more or less advanced stage of decay 

 commencing in the pith and proceeding thence into the 

 wood around. This decay consists in a gradual rotting 

 and oxidation — i.e. combustion — of the wood-substance, 

 essentially similar to the decomposition which all wood 

 undergoes sooner or later, especially when exposed to 

 alternating conditions of drought and moisture in 



FiG. II. 



