THE DIFFERENT PEOPEETIES OF WOODS 193 



a marked influence on the durability of the wood. Many claim 

 if posts are cut in winter, when the "sap is down," they will 

 be more durable than if cut in summer. In the winter time 

 the wood of trees contains large amounts of starches and 

 sugars and other food materials stored in the wood. So a 

 post would naturally be more durable if cut in summer than 

 in winter. There is no meaning to the expression when the 

 "sap is down," for the sap never moves down the wood of 

 the tree as we have learned, and there is actually more moisture 

 in a tree in winter than in summer, because of the less trans- 

 piration taking place from the tree. If cut in winter posts 

 dry out slowly and do not season check so deeply as when 

 cut in summer. This may have some effect on the durability. 

 It is claimed by many that well seasoned posts will be more 

 durable than posts set green. Some claim, also, if a post is 

 set upside down it will last longer than if set with the large 

 end in the ground. In all probability these will have little 

 effect on the durability of the wood. Posts cut early in the 

 spring are easier to peel than if cut at any other time. 



The following table shows the relative durability of some 

 of the common woods : 



Strength. — Strength in wood varies with the density or 

 weight. Light woods lack the strength of heavy woods. 



