MR WITHERS. 



225 



Consideration of the difference of tension of the 

 concentric layers, from the difference of disposition 

 to contract hy drying, modified hy the diflPerence of 

 position in which these layers may stand, when sup- 

 porting weights and hearing strain, with the various 

 quahties of timber of the same kind of tree, from 

 variety, age, soil, climate, or from being taken from 

 near the outside or heart, or butt or top, will, we 

 think, account for the contrariety of results which 

 unphilosophical experiments have afforded. 



