Page:Popular Science Monthly Volume 71.djvu/28

22 composed of 42 twisted pairs of No. 18 cotton-covered wires, which were wrapped together and drawn into a lead pipe one inch in diameter. Then a mixture of melted paraffine and rosin was poured into the pipe, the whole forming a solid mass on cooling. This cable was about 600 feet in length and was suspended from three heavy iron wires by loops made of No. 14 iron wire.

At one of the telephone conventions C. N. Fay stated that

the use of cables for telephone purposes in Chicago began in 1879, when a 50-wire Brooks oil-pipe cable, 925 feet long, was placed in the Washington Street tunnel under the bed of the Chicago River. The conductors were made of No. 20 copper wire, insulated with cotton, and drawn through an iron gas-pipe previously polished smooth on the inside. The ends of the pipe were elevated, and upon each end was placed a reservoir capable of holding three or four gallons of paraffine oil. After the pipe was put in place, the cable was drawn through. Paraffine oil was then poured into the reservoirs until the pipe was filled from end to end and both reservoirs were full, when the caps were screwed on and the whole made tight. There was a loss of oil from evaporation and leakage through the pipe, requiring a refilling about once in six months. In 1880, a 75-pair cable of similar construction, 450 feet long, was placed in the LaSalle Street tunnel under the Chicago River; another one being placed in the spring of 1881. In 1884, all the oil-pipe cables were in good and satisfactory working condition. . . . . The first aerial cable was put up in Chicago in September, 1882, and was a 50-pair Patterson cable 1,350 feet long.

Six Brooks oil-pipe cables were in use early in 1880 in Milwaukee. Each cable was about five hundred feet in length and composed of fifty single conductors, and all were considered "very satisfactory."

It is of historical interest to note that in April, 1843, S. F. B. Morse detailed to the Secretary of the Treasury the specifications under which forty miles of a four-conductor lead-covered cable would be made. Each wire was to be

once covered with cotton thread, to receive two coatings of shellac varnish; then wound with a different colored twine to designate, in case of necessity, any particular wire in any part of the course. The four lengths are then laid side by side and bound together in a single cord by another winding of cotton twine. The conductors thus prepared are ready to be introduced into the lead pipe.

When the underground question first came up, the leading telephone companies made it clear to the authorities of the respective municipalities, that any hesitancy in removing overhead wires and placing them underground was not due to an unwillingness to make the additional and very large investment necessary, but to contending with obstacles that then appeared insurmountable. There was no practical underground system suitable for telephone distribution in American cities. Several experimental systems were being promoted, but all appeared to possess little practical value. One promoter laid a half-mile of his pipe underground and then invited a large number of telephone,