Page:Ballantyne--The Battery and the Boiler.djvu/74

 'slack' for the inequalities of the bottom. Its cost will be £700,000, and the whole when finished will weigh 7000 tons."

Poor Robin's mind had, of course, been informed about ton-weights at school, but he had not felt that he realised what they actually signified until the thought suddenly occurred that a cart-load of coals weighed one ton, whereupon 7000 carts of coals leaped suddenly into the field of his bewildered fancy. A slightly humorous tendency, inherited from his mother, induced 7000 drivers, with 7000 whips and a like number of smock-frocks, to mount the carts and drive in into the capacious hold of the Great Eastern. They turned, however, and drove instantly off his brain when he came into the august presence of the cable itself.

The central core of the cable—that part by which the electric force or fluid was to pass from the Old World to the New, and vice versa, was made of copper. It was not a solid, single wire, but a strand composed of seven fine wires, each about the thickness of a small pin. Six of these wires were wound spirally round the seventh. This was in order to prevent what is termed a "breach of continuity," for it will be at once perceived that while a single wire of the core might easily break in the process of laying the cable, and thereby prevent the flow of electricity, the probability of the seven small