[D8627ZAL], Letter from Samuel Insull to John Canfield Tomlinson, November 26th, 1886


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[D8627ZAL], Letter from Samuel Insull to John Canfield Tomlinson, November 26th, 1886

Editor's Notes

The Edison system of underground conductors is composed of an iron pipe in which is placed three rods of copper, which are insulated by a compound which is forced into the pipe hot. These lengths of tubing average about 20 feet and are joined by means of a junction box with flexible copper joints inside said box, the box being filled with compound after the junction is made. ##The Callender system is composed of three distinct cables. These cables are made in continuous lengths, are laid in a wooden box, which box is filled in with a compound very much the same as that used in the Edison tubes. Owing to the fact that in the case of the Callender Co. they dispense with an outside metallic shield, such as a tube used in connection with the Edison System, and also owing to their cables being made in continuous lengths, the cost of construction and laying is very much less than the Edison System, probably from 18 to 20%. The Edison people have some doubts as to the Callender System being as reliable as the Edison tubes, the fact that it is so much cheaper will of course lead to its general adoption. ##I may mention that at the time the Machine Works made the working arrangement with the Callender Co., the Machine Works were figuring on a continuous cable for feeders, as it is the general opinion manifested by our people (outside of TAE) that a continuous cable is best adapted to our business, so far as feeders are concerned. ##The Edison tubes will continue to be used as mains, because it is so easy to make connection with each house, the junction boxes, which occur every 30 feet in the tubes, forming a natural outlet to each house for the service conductor to connect the house with the general system of mains.




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Thomas A. Edison Papers, School of Arts and Sciences, Rutgers University
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