BITUMINISED FIBRE CONDUIT.
For one of the safest and most perfect insulators for electric wires, and one which would take away all risk of explosion and consequent fire, the vitrified clay conduit was long regarded as ideal. And yet it has always been recognised as open to many objections. Some of these are to be found in its short lengths, which, by multiplying the joints, increase the cost of insulation. Another is its porousness. This causes it to accumulate gases which, traveling through the system, greatly render explosion possible. and the admission of moisture and water—the best of all conductors. It is also fragile, and, therefore. liable to break in handling, and of great weight, which entails heavy freight charges. What is likewise a great disadvantage is that the cement on the inside of the joints, which occur at short intervals, makes it difficult to draw the cable through, and also abrades and scrapes its covering to its great injury. As a substitute is proposed an electrolysisproof bituminised fibre conduit, which has for some time been used in California and the Southwest for irrigation purposes. This conduit is made of especially prepared paper, saturated under pressure with a bituminous composition, and built up—also under pressure—of a number of laminations. This gives a perfectly smooth interior and exterior surface. While the greatest length of the vitrified clay conduit is three feet, and the actual average in use about eighteen inches, the fibre conduit is made in standard lengths of seven feet. and. while the possible diameter of the clay conduit is limited to three and four inches, the fibre conduit comes in sizes ranging from one to ten inches. The expense of installation favors it by some fifteen per cent, to twenty-five per cent., not so much because of the actual material being cheaper, but. because any unskilled laborer can lay it at $2 a day instead of the $5.20-a-day bricklayer or mason. As an irrigation pipe it has been found to give absolutely no leakage and to be of wonderful endurance. Filled with water for days, it might be as many days without a drop in it, and yet remain perfectly watertight, and be in nowise impaired. In the same way it can keep water out the great requirement in electrical work, In all electroylsis tests it has come forth unscathed under the same conditions that have effectually destroyed the other conduits. Its ability to withstand exceptionally high voltages has been fully demonstrated, even 50,000 volts not being sufficient to break it down. This bituminised conduit was first tried, experimentally. in California, six years ago, as a conduit, and, having proved satisfactory in every way, it was then introduced into Chicago and the Middle States, and later—about a year ago it was brought East. It is now in general use in California, in extensive use in the Middle States, and is making fine progress in the East. It is also verv extensively used by the United States government, by telephone, telegraph, traction mining companies, and electric companies (among them the Edison Electric company). Besides being so cheap as to render it gainful under municipal ownership, its use avoids the danger from overheated wires—the fireman s great bugaboo in fighting a fire—and of fires from that source and of general breakdown and ntixups during snow, wind, or electrical storms, as well as the necessity for monstrosities in the shape of telegraph poles erected in the public streets and on the public highways. while under ground, in the subways, each cable having its own conduit, there can he no danger of trouble arising from fallen or crowded wires, and, therefore. no interruption to business.