POLES AND PILING 325 



most commonly used in preserving piles. On account of their sus- 

 ceptibility to treatment, reasonable cost, and other qualifications such 

 as strength, shape and availability, the southern yellow pines, western 

 yellow pine, and Douglas fir are preferred for treated piling. 



Properly preserved piles have been known to last from twenty-five 

 to thirty-five years in waters containing marine borers. The cost of 

 creosote treatment is usually from 3 to 7 cents per cubic foot. 



SUBSTITUTES FOR POLES AND PILING 



With the gradually increasing cost of wooden poles the large com- 

 panies which use the greatest number have naturally investigated the pos- 

 sibility of other materials. In many cities the telephone and telegraph 

 lines are placed in underground conduits. 



The chief substitutes for overhead lines are concrete, reinforced con- 

 crete, iron and latticed steel poles and steel towers, the last named being 

 used to some extent for heavy transmission lines. 



Up to the present time these materials have not replaced the wooden 

 pole to any great extent and it is not likely that they will for some time 

 to come, for the following reasons: 



1. High initial cost that is scarcely justified in service rendered. 



2. Excessive weight and consequent difficulty and expense in 

 handling and transportation. 



Concrete and reinforced concrete poles are still in the experimental 

 stage of development, and all forms of substitutes lack sufficient length 

 of service to draw definite conclusions. 



Reinforced concrete, wrought and cast iron and steel piling have been 

 introduced to a much smaller extent than in the case of poles, so that little 

 is known of their possibilities. It is likely, however, that difficulties of 

 corrosion in case of iron and steel and cracking due to alternate freezing 

 and thawing with concrete piles, together with the objections given 

 above for pole substitutes, will render their introduction rather slow and 

 doubtful. 



BIBLIOGRAPHY 

 KEMPFER, W. H. Preservative Treatment of Poles. Bulletin 84, U. S. Forest 



Service, 1911. 

 Proceedings, American Wood Preservers' Association. Annual, 1910-1919, inclusive. 



Baltimore, Md. 

 SMITH, C. S. Preservation of Piling against Marine Wood Borers. Circular 128, 



U. S. Forest Service, 1908. 



Statistical Reports, U. S. Bureau of Census for 1905 to 1914, inclusive. 

 WEISS, H. F. Preservation of Structural Timber. McGraw-Hill Pub. Co., New 



York City: 1915. 



