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Page:Popular Science Monthly Volume 70.djvu/522

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IX. Telephone Line Construction.

IN 1876 the wires used for telegraph, circuits were usually of iron or steel, because the tensile strength permitted of long spans and comparatively long sag. At that period hard-drawn copper line wire was unknown, and it is problematical whether the volume of traffic passing over the average telegraph wire at that time, outside of the main trunk lines, would have justified the heavy initial investment required to string copper circuits. Thus it came about that iron and steel wires were naturally adopted for telephone lines. About that time George B. Prescott wrote that

a very short experience with, copper line wires both in this country and in Europe, proved that this metal was altogether unsuitable for the purpose, its sole recommendation consisting in its superior conductivity, and it was, therefore, soon replaced by iron wire of large diameter.

But T. B. Doolittle proved how fallacious that theory was, by producing a hard drawn copper wire in 1877, that, as stated in Chapter V., proved of inestimable value to telephone interests the world over.

This failure on the part of soft drawn copper wire to satisfactorily serve as line wire was due to the unpleasant habit it had of not staying where it was placed; it lacked the physical stamina to support itself, and would break with its own weight. This fact was well known to telephone men. Yet few perceived the merit in Mr. Doolittle's improvement, or took kindly to it until forced to do so by later conditions. In 1880, three years after Mr. Doolittle's experimental hard drawn copper line had been strung in Ansonia, Connecticut, a telephone line gang started to string a toll circuit between Hartford and New Britain, but completed less than five miles. This circuit consisted of one No. 18 soft drawn copper 'office' wire, having a double braided cotton covering saturated with paraffine; but by reason of the long spans between the poles the sag was sufficient to cause the small soft wire to break with its own weight. Thus, after spending several days in rejoining broken ends, the circuit was abandoned, and iron wire strung in its place.

In cities and wherever the iron circuits were subjected to the destructive effects of atmospheric action, especially where much bituminous coal was used, oxidization shortened the life of the circuits in