370 PROPERTIES AND USES OF TIMBER. 



moisture to evaporate before applying the wood to 

 use. If unseasoned wood be cut into deals, and 

 formed into any piece of workmanship, for instance 

 a door, the shrinking produces open chinks in the 

 joints, and not unfrequently splits the deal. This 

 is particularly the case with fir- wood of every kind, 

 but especially the larch. 



Another circumstance is worthy of remark, in re- 

 gard to the application of wood in general to useful 

 purposes. The outer parts of the tree, nearest the 

 bark, commonly termed the Sap-wood, is weaker, 

 and much more liable to rot, than the interior part, 

 or heart-wood of the tree. Sap-wood is of less im- 

 portance in old trees than in young ones, and in 

 hard wood than in firs ; but, in general, where wood 

 is used for purposes requiring great durability, it 

 should be planed off, as the greater part of it usually 

 is in squaring the logs. In general it may be easily 

 known, both by a difference in colour (being 

 whiter), and a difference in texture, from the heart- 

 wood. In examining old floors, it will frequently 

 be seen, that the edges of the deals are destroyed by 

 the dry-rot, while the centre is quite sound ; a prac- 

 tical exemplification of the fact here mentioned, the 

 edge being easily seen, in such cases, to be part of 

 the sap-wood. 



