PROPERTIES OF WOOD AND THEIR USES 59 



and more durable and possess greater fuel value. The 

 lighter woods are inclined to season readily and to 

 work easily, but usually lack strength and durability. 



Strength A wood is said to be strong when it re- 

 sists pressure or tension from various sources; the 

 pressure may be applied either with or across the grain 

 and different species show a varying power of resistance. 

 Both longleaf pine and white oak resist pressure with 

 the grain especially well and hence they can be used 

 to advantage as columns where great weight must be 

 supported. Other species show varying resistance to 

 different kinds of strains and the Forest Service Timber 

 Testing Laboratory at Madison, Wisconsin, has made 

 many experiments on all kinds of woods to find out the 

 uses to which they are best suited. 



Within the same species, the strength of wood is due 

 to condition, its freedom from knots and cracks and 

 also to the amount of water it contains. Freshly cut 

 timber is weak in comparison with the same stick when 

 thoroughly seasoned. The weight of wood is generally 

 a good measure of its strength, as woods that are heavy 

 when dry contain a large amount of wood fiber and 

 consequently break or crush with difficulty. 



Other properties such as toughness, cleavability, 

 elasticity, etc., might be mentioned. Hickory is es- 

 pecially valuable for use in wagon making on account 

 of its hardness and toughness and from the elastic white 

 ash are made much of athletic equipment so dear to 

 the heart of the outdoor boy or man. Baseball bats 

 and snowshoes are made from ash, as it combines tough- 

 ness and elasticity to a marked degree. 



Defects. Wood, however, is rarely perfect and may 

 contain defects which will seriously impair its strength 

 or prevent its use for a given purpose. Knots are per- 



