3i8 THE TIMBERS OF THE WORLD 



surface, but most actively at the two ends ; when the bark is left on the 

 log, evaporation is excessively slow, save where there are cracks. As the 

 moisture is lost at the surface, the drying superficial wood receives water 

 from the interior, but sooner or later a time comes when it receives less 

 than it loses ; the log then, when protected from outside moisture, 

 assumes a condition in which it is relatively dry externally and relatively 

 moist in the middle. This condition may endure for years, possibly for 

 centuries in the case of dense woods : for instance, thick walnut trunks 

 when cut open after being stored indoors for years are found to be 

 thoroughly wet in the middle. Even if such logs are described as seasoned, 

 their wood cannot be so described. If the log be cut up, the resulting 

 pieces, including the centre wood, being moist, will shrink and are liable 

 to warp and split in the same manner as similar unseasoned pieces. 

 Yet such " seasoned " logs or large beams are very different in properties 

 from freshly-felled specimens. This is clear when it is remembered that : 



(i) Deformation, warping, and cracking are, in the beginning, caused 

 by unduly rapid drying at the surface. 



(2) Dry wood is stronger than wet wood, and in mechanical structures 



the important matter is to have the external part strong. 



(3) Wood-destrojdng fungi causing rot, gain entrance solely through 



moist wood. 



(4) It is possible that wood seasoned slowly is superior in mechanical 



properties to wood rapidly seasoned (it is also certainly less 

 liable to split during seasoning). 



Thus the " seasoned " beam used as such, or as an upright for internal 

 work, is stronger, less liable to deformation, splitting, and decay. Yet it 

 is obvious that logs or large beams thus seasoned are superior as a whole 

 to fresh wood only under circumscribed conditions and for special 

 purposes. If the wood is to be used whole out-of-doors, in a moist 

 climate, it may often be inferior to unseasoned wood because it will be 

 more liable to swell and undergo deformation and splitting. Again, if 

 it be subsequently cut into thin or small pieces, and these be used at once 

 for internal work, the wood is far inferior to such pieces seasoned in their 

 small state. 



Laslett, who had wide and prolonged experience, wrote : " The most 

 effectual way to preserve good timber is to partially season it in as natural 

 a way as possible before working it up, and to give it simply the protection 

 when brought into use which all other materials require to keep them 

 from perishing. . . 



" My experience of the approximate time required for (partially) 

 seasoning timber under cover, and protected from wind and weather, 

 is as follows : 



