400 HORTICULTURE, FORESTRY, FLORICULTURE 



cient after decay has progressed for several years. Obviously such 

 large posts are unnecessary if proper preservative treatment is given, 

 and, since the cost of treatment increases rapidly with the size of the 

 post, there is much advantage in using comparatively small ones. 

 For instance, a well-treated line post need not exceed 5 inches aver- 

 age diameter. 



The form of the post, whether it is round or split, may influence 

 the efficiency of the treatment. A split post necessarily has heartwood 

 exposed to the air. With some woods this is immaterial ; with others 

 the heartwood can not be impregnated, and untreated heartwood will 

 prove inferior in durability to properly treated sapwood. Therefore, 

 only round posts of the latter class should be used. In general, the 

 heartwood that is highly colored, such as that of oak and yellow pine, 

 is practically impenetrable. 



The tops of the posts should be cut obliquely to shed rain water. 

 A bevel made with an ax is preferable to one made with a saw, 

 because it is smoother. Beveling is particularly important if the tops 

 of the posts are not to be treated. Bark retards or prevents the 

 penetration of the preservative into the wood. It also uselessly 

 increases the cost of treatment by itself absorbing oil. Peeling the 

 posts before treatment is, therefore, necessary. Even the papery 

 inner bark should be carefully removed, especially in the case of 

 pine and basswood. Thorough seasoning should always precede 

 impregnation. Even air-dry wood is unfit for treatment after a 

 heavy rain, and when thus saturated should be permitted to dry for 

 at least three days of good seasoning weather. 



Under favorable conditions the average period required to 

 season posts is five weeks, but this period varies widely, according 

 to the kind of wood, the season of the year, and climatic conditions. 

 A simple method of determining the degree of seasoning is to weigh 

 a few representative posts every few days. As a rule, an air-dry con- 

 dition is reached when the loss of moisture is less than 1 pound per 

 post (of 5 inches average diameter) during five days of good season- 

 ing weather. 



Application of the Preservative. It is well known that differ- 

 ent woods vary greatly in weight and strength. They also differ 

 considerably in the ease with which they absorb the preservative; 

 so that each species requires a different treatment if best results are 

 to be obtained. In the experiments conducted by the Forest Serv- 

 ice and its cooperators the purpose has been to determine the best 

 treatment for various woods. The investigations have also indi- 

 cated the relative ease of treatment of the different woods. Two 

 methods of treating were employed. In some cases but one tank 

 was used, and only the butts of the posts were impregnated, though 

 two tanks were used in creosoting most of the woods. In the second 

 method only the butts were immersed in the hot bath, while the 

 whole posts were submerged in the cold bath. 



Most species will absorb too much creosote if a very long treat- 

 ment is given. Therefore, to make the treatments economical the 

 absorption must be limited to 0.4 gallon per post if only the butt ia 



