4 BULLETIN 519^ U. S. DEPAETMENT OF AGRICULTUEE. 



In comparing the 1911 purchase of poles with the 1915 purchase, 

 an increase of 832,966 poles under 20 feet in length was reported, 

 wliile the number between 20 feet and 30 feet showed a decrease of 

 330,375. Tlie total number of poles purchased in the other lengths 

 did not vary greatly from the 1911 figures, slight increases in all 

 being reported for 1915. 



PRESERVATION. 



One of the most important factors in determining the value of a 

 pole is its abihty to resist decay in contact with the soil. While 

 durable woods are generally preferred as pole timbers, there is a 

 tendency toward pm-chasing other species which are not as dura- 

 ble, but which can be rendered less liable to decay by preservative 

 treatment. 



In the treatment of poles several methods are used. Among these 

 ai'e the brush treatment; the open-tank treatment, in wliich the 

 poles are stood on end in open tanks or vats containmg the preserv- 

 atives; and the pressure treatment, in which the poles are placed 

 in cylinders into which the preservative is then run and pressure 

 apphed to force it into the poles. Much progress is being made in 

 the butt treatment of cedar poles by the open-tank method, which 

 is being used extensively in Idaho, Washington, and Cahfornia, and 

 in the Minneapohs and Chicago districts. A considerable propor- 

 tion of the cedar poles sold receive a butt treatment. 



The Forest Service did not request information relative to the 

 number of poles treated by the various railroads and other compa- 

 nies reporting the purchase of poles. It has, however, obtained 

 information from 102 treating plants operating tln-oughout the 

 United States. These plants reported a total of 125,639 poles 

 treated in 1915, which is estimated to be about one-haK of the 

 actual number subjected to treatment. A large number are treated 

 merely by applying the preservatives with a brush, and these were 

 not reported. 



It is impossible to submit a tabulated statement showing the 

 number of poles treated by the different kinds of preservatives, 

 owing to the lack of detailed information obtained. In treating the 

 poles in 1915 the principal preservative reported was creosote oil, 

 the average absorption being about 11 pounds to the cubic foot. 

 About 85 per cent of the poles treated were yellow pine, while others 

 reported were western red cedar and Douglas fir. 



The cost of treating poles varies according to the kind of wood 

 treated, kind and quantity of preservative used, and process em- 

 ployed, but experience has demonstrated that the adoption of a polo- 

 treating pohcy generally proves economical and insures added life 

 to the poles in service. 



WASHINGTON : GOVERNMENT PRINTING OFFICE : 1917 



