a Re, 
4, BULLETIN 519, U. S. DEPARTMENT OF AGRICULTURE. 
in comparing the 1911 purchase of poles with the 1915 purchase, 
an increase of 832,966 poles under 20 feet in length was reported, 
while the number between 20 feet and 30 feet showed a decrease of 
330,375. The 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 ability to resist decay in contact with the soil. While 
durable woods are generally preferred as pole timbers, there is a 
tendency toward purchasing other species which are not as dura- 
ble, but which can be rendered less liable to decay by preservative 
treatment. i 
In the treatment of poles several methods are used. Among these 
are the brush treatment; the open-tank treatment, in which the 
poles are stood on end in open tanks or vats containing the presery- 
_atives; and the pressure treatment, in which the poles are placed 
in cylinders into which the preservative is then run and pressure 
applied 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 Idahc, Washington, and California, and 
in the Minneapolis and Chicago districts. A considerable propor- 
tion of the cedar poles sold receive a butt treatment. 
The Forest Service did not request mformation 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 throughout the 
United States. These plants reported a total of 125,639 poles 
treated in 1915, which is estimated to be about one-half 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 showig 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 bemg 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 pole- 
treating policy generally proves economical and insures added life 
to the poles in service. 
WASHINGTON : GOVERNMENT PRINTING OFFICE : 1917 
