INJURIOUS INFLUENCES 77 



from the centre towards the outside, the clefts 

 being widest at the sapwood. Cup-shake 

 renders much of the timber of the trees so 

 affected valueless for constructive purposes. In 



Star-shake. 



Cup-shake. 



soft-wooded trees like the poplar and Spanish 

 chestnut, cup-shake is brought about during 

 stormy weather, as the stem, in bending back- 

 wards and forwards to the blast, causes the con- 

 centric layers of wood by alternate compression 



