234 PRINCIPLES OF AMERICAN FORESTRY. 



TABLE SHOWING RANGE OF DURABILITY OF FENCE- 

 POSTS IN MINNESOTA (Air dry ) 



Red Cedar 30 years 



White Cedar (quartered 6-inch face) 10-15 years 



White Oak (6-inch round) 8 years 



Red and Black Oak 4 years 



Tamarack (Redwood) 9 years 



Elm 6-7 years 



Ash, Beech, Maple 4 years 



Black Walnut 7-10 years 



White Willow, 6 inches in diameter, peeled and dried. . . 6-7 years 

 Catalpa 20 years 



Curing is one of the most important processes in its 

 effect on the durability of wood. Well cured wood resists 

 decay far better than fresh wood, because it contains an 

 insufficient amount of water for the growth of fungi. 

 Green wood covered with paint before it is dry is often 

 destroyed by dry rot, since this fungus finds abundant 

 moisture under the paint, and the protection which was 

 intended for the wood really protects its enemy, the 

 fungus. Paint and other wood-protecting compounds 

 are efficient only when they are applied to dry material, 

 which they preserve by protecting them from moisture. 

 But fence posts or other timber to be used in moist places, 

 if well cured, will, even if not protected, last much longer 

 than fresh cut timber. The amount of moisture in wood, 

 then, is the most important factor in influencing its dura- 

 bility. 



Timber is Best Cured Under Cover, where it is pro- 

 tected from the sun and the full force of the ^vind, but has a 

 good circulation of air. If piled in the open, it is a good 

 plan to shade it. When piling green or wet timber, 

 place lath or other strips of wood of uniform size under 

 each log, post or tie. In piling sawed lumber the lath 

 should be placed at the ends, as in this position they in a 

 measure prevent checking on the ends. 



