1905 



FORESTRY AND IRRIGATION 



37 



must fall. Chestnut and white cedar 

 have been found, among available 

 woods, most successfully to resist de- 

 cay; but the life of the former is only 

 from twelve to fifteen years, and of the 

 latter ten to twelve years. The co- 

 operative study of the Bureau is for 

 the purpose of extending, if possible, 

 this time. 



The experiments already made by 

 the Bureau show conclusively that 

 poles can be subjected to a preserva- 

 tive treatment which insures material- 

 ly lengthened service. This treatment 

 consists in impregnating the wood 

 with antiseptics which prevent the 

 growth of the fungi that cause decay. 

 The treatment of telegraph and tele- 

 phone poles, when attempted at all in 

 this country, generally has been ap- 

 plied to the whole pole, requiring the 

 use of air-tight cylinders 100 feet long 

 or more. In these the poles are sub- 

 jected to live steam for some time, 

 when a vacuum is created. Creosote 

 is then run in and pressure applied to 

 force it into the wood. Manifestly 

 this is a laborious process. Yet for 

 telegraph and telephone poles only 

 about one foot of the entire length 

 needs to be made immune from fun- 

 gus. If this foot at the fatal ground 

 line can be preserved from decay, the 

 rest of the pole will take care of itself. 

 Experiments will now be made in 

 treating the butts of the poles for a 

 distance of about eight feet, thus car- 

 rying the antiseptics just beyond the 

 zone of decay attack. The creosote 

 method will be used and dead oil of 

 coal tar forced through the butt of the 

 pole. 



The telegraph companies have made 

 little use of preservative treatment. 

 They employ millions of poles on their 

 various lines, and it would be a tre- 



mendous economy to add even a few 

 years of service to the life of each pole. 

 But there will be another large saving 

 both to them and to the forests 

 through preservative treatment. To 

 provide a good margin against decay, 

 poles are now much larger than de- 

 manded by the strain upon them. It 

 is expected that decay will quickly eat 

 away a furrow around the pole at the 

 ground line, and the diameter of the 

 pole at that point is gauged to allow 

 for this weakening process. When it 

 is known that decay, in a certain num- 

 ber of years, cuts the diameter from 

 perhaps twelve to eight inches, and 

 that below eight inches the weakened 

 pole falls, the course to be pursued is 

 obvious. Antiseptics prevent, for the 

 time of their effectiveness, the starting 

 of decay, and thus permit at the outset 

 the selection of an eight-inch diameter 

 rather than a twelve-inch. The four 

 inches saved represent a tremendous 

 difference in the size and age of trees 

 used for poles. Both the companies 

 and the owners of forests will be great 

 gainers by this economy, with its 

 shortening of the length of time neces- 

 sary to grow a pole. 



Another feature of the co-operative 

 work will be treatment of cross-arms. 

 The companies have been treating 

 them, but report too much absorption 

 in some cases and not enough in oth- 

 ers. The Bureau will more carefully 

 grade the different kinds of wood, and 

 treat each class separately. In this 

 way it is expected to secure a more 

 equal absorption and more satisfactory 

 results. These are the main points 

 covered by the contracts, though in ad- 

 dition the Bureau will furnish infor- 

 mation on the supply of pole timber 

 and such general advice as may be 

 suggested by the co-operative work. 



