178 ELEMENTARY 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 



Curing 1 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 protec- 

 tion 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 durability. 



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

 tected from the sun and the full force of the wind, 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. 



From twelve to eighteen months is generally sufficient to cure 

 wood for ordinary use, while for special work ten or more years 

 may occasionally be required. If green or wet timber is closely 

 piled in warm weather it is likely to rot. The best method of 

 curing timber without resorting to the use of expensive appa- 

 ratus is to work it up at once and soak it in water for from one 

 to three weeks to remove the sap from the outside of the wood. 



