Popular Science Monthly/Volume 3/May 1873/Ocean-Cables

The same firm laid an unprotected core from Varna to the Crimea, and it lasted until the winter set in; it is frequently said that it was cut by order of the French commander-in-chief, but there is no proof of this, and I am not disposed to believe it. This causes the voltages induced by a magnetic field between the shield and the core conductor to consist of two nearly equal magnitudes which cancel each other. Any current-carrying conductor, including a cable, radiates an electromagnetic field. The first cable ever manufactured with due regard to the principle of careful supervision, testing under water, and being retained quietly in that condition until it was laid, was the Malta and Alexandria cable, laid in 1861. This cable was submerged in too shallow water, for many miles in less depth than 20 fathoms; the result was the frequent recurrence of fracture from being rolled about by the surf, and yet this cable was only finally abandoned last year; not because it could not be kept in repair, but because it was too expensive to keep in order. The loss of cables was found to be attributable to the following causes: First, and the most important of all, from imperfect manufacture, resulting without doubt, prior to this date, from inexperience of the materials for insulating the copper wire, and from ignorance of the fact discovered by Prof. Thomson about 1856, viz., that some kinds of copper wire were no better than iron for the purpose of conductivity, and that it required carefully-selected copper to give the desired standard, which may be represented by a copper wire one-tenth of an inch in diameter, being equal to an iron wire one-third of an inch in diameter for electrical purposes.

Tin, gold, and silver are much less prone to oxidation than copper, which may lengthen wire life, and makes soldering easier. Beyond this, there are particular cable designs that minimize electromagnetic pickup and transmission. An electrical cable is an assembly of one or more wires running side by side or bundled, which is used as an electrical conductor to carry electric current. The Red Sea and Indian cables are said to have been imperfectly manufactured and laid too taut, but they were not tested under water from the time of manufacture until they were placed at the bottom of the sea, and this one grand omission, largely due to inexperience, is enough, without the recriminatory points, to condemn to loss and failure any cable whatever. The first solution to these problems is to keep cable lengths in buildings short since pick up and transmission are essentially proportional to the length of the cable. The necessity of living in sanitary localities, in moral and well-regulated communities, where children can have all the advantages of church and school, of light and air, becomes more and more evident as municipal governments undertake to solve the problems that are pressing upon them.

The crowding of streets with the transportation essential for the movement of goods increases with great rapidity, but when the crowding is augmented, perhaps doubled, by the presence of the means of transporting passengers, the difficulties involved are almost appalling. THIS is by no means a new subject for investigation, but in the present day I am certain that it will be instructive to many among the thousands who are now interested in this class of property to have their attention briefly called to all that has been done to make submarine cables a sound property. Ribbon cable - Useful when many wires are required. I have said already that the committee called attention to the remarkable fact that, in almost all cases, small cables have been found liable to mishaps, while the heavier the cable the greater had been its durability. Mr. Woodehouse, the engineer who laid this core, said in his evidence he "should not advise anybody to lay so light a cable across the Atlantic, because so small a strain would break it. If it is once safe at the bottom, perhaps it may rest." Mr. Newall said he thought it folly to lay any thing excepting unprotected core.

He would cover the copper with India-rubber, protect this core with steel wires vulcanized, the whole then passed through heat; thus insulating all the wires, he would make the cable in one length, and have no joints. There is no instance yet of a well-manufactured heavy cable breaking or giving out in deep water after it has been carefully laid free from defects; but there may be much due to the external covering keeping it quiet; there has assuredly been a great deal due to the external covering in the successful submerging, and there is no experience whatever to justify the assumption that an unprotected core would last, even if laid. There appear to have been mechanical difficulties in keeping the copper conductor in the centre of the insulating medium, so that the copper was sometimes found to be almost visible under the light film of gutta-percha which covered it. The first thermoplastic used was gutta-percha (a natural latex) which was found useful for underwater cables in the 19th century. These and many other examples have established the principle that no cable should be laid without first obtaining an accurate survey of the approach to the coast and landing-places, with accurate soundings over the intended route, and as much knowledge as possible of the nature of the bottom.

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