FENCING 227 



Wood posts. Although there is no sharp dividing line, 

 wood posts may be considered as of two classes, those which 

 have a naturally long life, and those which in their natural 

 condition last but a short time, but the life of which can 

 be prolonged by the application of some preservative treat- 

 ment. The decay of timber is caused by the work of fungi. 

 These fungi feed on substances in the wood and destroy 

 by the process known as rotting. In order that they may 

 live they require, in addition to wood, heat, air, and moisture. 

 The wood which has each of these requirements in the 

 proportion most conducive to their growth decays most 

 rapidly. 



Durability. The life of a fence post depends upon the 

 kind of wood, age, rate of growth, percentage of sapwood, 

 character of soil, and the variability of moisture where it is 

 used. Wood that is continuously under water or in a dry 

 place does not decay. It is the change trom one medium to 

 the other that aids the decaying process. The weakest point 

 in a post is at or immediately under the surface of the ground, 

 where an alternate wetting and drying occurs. Frequently 

 posts that are sound a foot under or above ground will break 

 off at the surface. Posts that are not to be used immediately 

 upon cutting or are to be seasoned for further treatment 

 should be peeled and piled on other timbers placed on the 

 ground, the posts being laid in layers at right angles to one 

 another a sufficient distance apart to permit the free circu- 

 lation of air. Bark and sapwood tend to cause rapid decay. 



The average life of air-dried posts is as follows: 



Years Years 



Red cedar 30 Ash 5 



Black locust 22 Maple 5 



Catalpa 20 Red or black oak 5 



White oak 15 Birch 4 



Black walnut 15 Basswood 4 



White cedar 10 Jack-pine 4 



Tamarack 8 Cottonwood 4 



Elm 7 Aspen 4 



White willow 6 



