Morning journal and courier., 1884-06-27
Underground Wires.

What is Claimed for & New Invention. From the Philadelphia Press.l
 In back room on the second floor of 8 building in Walnut street there are on exhi- bition appliances for underground electricity which, their owners believe, will entirely rev.
 olutionize the present systems and bring
 about speedy burial of all kinds of electric | wires, whether they are for telephones, tele
 graphing or lighting. The system exhibited is the property of the Union Electric Under
 ground company of Chicago, and it includes
 three patents, the inventions of H. B. Cobb, of Wilmington, Del. The greatest difficult | ties underground inventors have had to con tend with has been the running of electric wires in the same conduits with the wires for telephone and telegraph lines. The latter currents being so weak were to a great ex- l tent made useless by the induction from the | former. It seemed that the only way to ob- viate this was the laying of conduits with separate com partments, but MT. Cobb, by his system, has made It possible, it is claimed, | for every kind of wire to be punched in a | single tube. The wire itself is said to be cheaper than that hitherto used. The con | duits, too, are not expensive
 The wires are placed in single tube like gas or water main. The diameter of this | tuba is ten inches, and it will hold 700 wires It is made of metal called kalamine, | mixture of lead and tin that resists the chemical action to which electric conduit l is subjected. This conduit can be laid at cost of $S, GOO mile. On each side of the conduit run tubss, two inches in diameter, l and with capacity of fifty wires. They are | intended to hold the wires that run for short
 distances and at regular intervals there are joints by which connection can be made with any house along the route. This is device which overcemes the necessity cf tapping the main conduit.
 The circular tube system is not a new one to electricians It is used almost exclusively in London where all the wires run under ground, and are coated with gutta percha.
 MT. Cobb, however, claims to have improved even on the London system. Instead of his
 wires being covered with an insulating coat from which they canpot be withdrawn, they run through tiny pipe, a little smaller than the familiar maccaroni tube, and this pipe is
 manufactured independently of the copper
 wire. When this tiny pipe has been tested
 the copper wire is forced into it by an ingen-
 ious machine, which is itself patented.
 Should the copper wire at any time need re-
 pairing the same machine withdraws 1t from
 the well fitting covering and then replaces 1t.
 This tiny tube, 1t is argued, is the best ln-
 sulator known. It is made of vulcanlzed
 rubber, three-sixteenths of an inch being its
 thickness, and one-sixteenth of an inch be-
 ing the diameter of the opening. The rub
 ber is covered with 8 thick electric deposition of copper The deposition surrounds the tube in accordance with the we'll known dis covery of Professor Henry, that a metallic
 shield, when employed between two separate ly insulated wires and in connection with the earth, prevents induction by carrying the surplus electricity into the ground. The success of the insulating tube has been de- monstrated by Professor Barrett, the city electrician of Chicago, who reported that the wire and tube, after having been in water for twelve hours, gave resistance to insula tion of 5000 meg ohms to ..the mile. The highest insulation secured by any previous invention was 1000 meg-ohms, result which electricians imagined would never be beaten. As it is. the best resistance usually obtained is 800 meg-ohms, which is regarded as thoroughly satisfactory.
 By the tube system each wire can be re- moved without the others with which 1t Is punched being disturbed in any way. The electric wire, which, on account Of the great insulation can be handled with perfect safe ty when the strongest current of electricity is running on it, costs less than $500 mile, or half the usual cost, and takes up about half the space that an electric light wire usu- ally occupies.