Figs. 921 to 929.—Pole construction tools. Fig. 921, long handled digging shovel; [fig. 922], digging bar; [fig. 923], crow and digging bar; [fig. 924], tamping and digging bar; [fig. 925], wood handle tamping bar; [fig. 926], slick digging tool; [fig. 927], post hole augur; [fig. 928], carrying hook; [fig. 929], tamping pick.
Wooden Poles.—On account of their size and straightness, various species of northern pine, cedar and cypress are especially suitable for large poles. Chestnut, which can be readily sawed and hewed is a very good material for smaller poles. Sawed redwood is extensively used in California.
Preservation of Wooden Poles.—The preservation of wooden poles employed in line work is a matter of importance. Decay of the pole at or near the soil line is caused primarily by various forms of bacteria or fungi, and in some cases by insects. Bacteria and fungi attack either dead or living timber. In the case of dead timber, such as that of poles, they attack the walls of the cells and cause the familiar rot or decay which eventually destroys the usefulness of the pole.
It is well known that the rapid multiplication or action of the bacteria and the growth of the fungi are induced by a certain per cent. of moisture and the heat of the sun, that is, the portion of the pole at or near the soil line is alternately moistened and dried. Therefore, in order to protect it against this action, it is necessary to sterilize the pole by the application of an antiseptic which will penetrate the pores of the wood.
Preservation Processes.—There are several processes which may be successfully employed for the preservation of poles or other exposed timber. The best known of these are the creosoting, burnettizing, kyanizing, carbolizing, and vulcanizing processes.
In England, creosoted poles showed no sign of decay at the end of 35 years of service. In the United States they have an average life of 22 years. In Europe impregnation with copper sulphate has been extensively used, but this impregnation must take place within a few days after cutting down the tree.
Uniformly good results have been obtained by impregnation with corrosive sublimate, involving simply immersion in the liquid from ten to fourteen days. German authorities state that the average life of such poles is about 17 years, compared with 14 years for natural or untreated poles.
The application of pitch and tar oftentimes results in more harm than good. It is authoritatively stated, however, that in Europe wooden poles are effectively protected by painting them with tar up to about 2 feet above, and down to about 1½ feet below the soil line. The painted parts of the pole are then covered with a cloth which after being nailed to the pole, is also painted with tar. Finally a zinc plated sheet of iron painted on both sides with tar, is placed around the cloth and tightened to the pole.
The saving due to the use of sterilized poles is 40 per cent. of the cost of unsterilized poles. The comparison is made on the following basis: Cost of pole, $5 each; sterilizing, $1.25; renewal of sterilized pole in 24 years, unsterilized pole, in 12 years.
