the pioneer telephone days, just as now happens thirty years later. The prevailing belief among the early telephone men was that iron wire would have an average life of from fifteen to twenty years. But it only required a brief experience to show that many iron circuits on city pole lines, even of extra best (E. B. B.), had an average life of less than four years, and that rapid rusting rendered some circuits worthless within three years.
For pole lines, chestnut was the principal wood used in 1876, though there were also many white and some red cedar poles used, and here and there a few locust and oak poles were occasionally utilized. The number of poles then placed to the mile varied according to the climate and the breadth of view of the owner. Ordinarily they ranged from fifteen to forty, the average in the northern states being from twenty-five to thirty, according to the downward range in temperature. As a rule, poles 25 feet in length answered every purpose, for there were no other lines to interfere, while 4-inch or 5-inch tops offered sufficient support to carry the few wires required in 1878-80.
Now-a-days the approved practise in building telephone trunk lines is to require selected heavy chestnut or cedar poles, not less than eight inches in diameter at the top, and with a corresponding heavy butt, and in length ranging from thirty to fifty feet, depending on the contour of the country and the number of circuits to be carried. From forty-four to fifty of these poles are placed per mile, while the depth that they are set in the ground ranges from five feet to nine feet, depending on the length of the pole and the character of the soil or rock.
It may be recalled that in the first circular issued by 'the proprietors of the telephone,' dated Cambridge, Mass., May, 1877, Gardiner G. Hubbard stated that
At the first glance the amount of material shown in that estimate may appear somewhat inadequate, judged by modern methods of standard pole line construction, calling for forty-four poles to the mile. Yet a moment's study will show that the proposed line was substantially planned, was far stronger and would probably possess far better talking qualities than some present day private lines. In an elaborate catalogue issued by a manufacturing telephone company in 1906, twenty-nine years after Mr. Hubbard's circular was issued, the following estimate appears: