WHY WOOD IS BEST 



993 



durable, or perishable, woods are made very durable. 

 Thus by treatment with creosote, zinc chloride, etc., 

 the hard but perishable beech and maples provide 



THE STOCK DRYING ROOM 

 Showing oak and hickory spokes and elm hubs, at Oakland, California. 



railroad ties of longer life than untreated white oak. 

 Toughness is the quality by which shocks and irregu- 

 lar strains are withstood. It is the opposite of brittle- 

 ness and differs from strength and hardness. The 

 classic example of toughness is a well-made wagon 

 wheel. The hub of elm resists the strain of the spokes ; 

 the spokes of hickory carry the twists of traffic, and 

 the mortised ends do not shear; the felloe of hickory 

 or ash maintains its shape against every deforming 



force. Hickory, white oak, white ash and rock elm are 

 all tough woods. By combining toughness with elas- 

 ticity and relatively light-weight white ash stands above 

 all others for farm implement handles, for vehicle 

 frames, and now for the structural parts of airplanes. 



Brittleness is usually a negative quality ; it may be 

 positive when a fracture is short and produces no long 

 splinters as tough wood when broken always does. It 

 is one of the qualities that make black walnut the pre- 

 ferred wood for gun stocks. 



Elasticity is the property of recovering an original 

 shape after deformation, and is usually a most valuable 



PRESERVATIVE TREATMENT 

 Brush treatment of telephone poles, showing method of application. 



quality. Oak makes a poor wagon tongue because it 

 is only moderately elastic and is apt to bend and stay 

 bent; but it makes a fine ship knee because it is hard 

 and strong, as well as tough and flexible, and when 



THIS IS THE BODY OF AN AUTOMOBILE BUS 

 White ash was used for the framework and interior finish. 



