Cable

Cable is either a large rope or a chain of iron links, chiefly employed on shipboard to suspend and retain the anchors. Rope cables are made of the best hemp or of wire, twisted into a mass of great compactness and strength. The circumference of hemp-rope varies from about 3 inches to 26. A certain number of yarns are laid up left-handed to form a strand; three strands laid up right-handed make a hawser; and three hawsers laid up left-handed make a cable. The strength of a hemp cable of 18 inches circumference is about 60 tons; and for other dimensions, the strength is taken to vary according to the cube of the diameter. Wire-rope has within comparatively recent times been to a certain extent taking the place of hemp for tow-line and hawsers on board ship. These usually consist of six strands, laid or spun around a hempen core, each strand consisting of six wires laid the contrary way around a smaller hempen core. The wires are galvanised or zinc'd, or else coated with a preservative composition. Wire-ropes are usually housed on board ship by winding them round a special reel or drum. Hemp cables, moreover, have for long been almost wholly superseded by chain cables; the introduction of steam on board ship having brought in its train the powerful steam-windlass wherewith to manipulate the heaviest chains and anchors required. Hempen and wire ropes are of course invariably used as tow-lines and for mooring vessels.

Chain cables are made in links, the length of each being, generally, about 6 diameters of the iron of which it is made, and the breadth about $3\backslash frac\{1\}\{2\}$ diameters. There are two distinct kinds of chain cables—the stud-link chain, which has a tie or stud welded from side to side, and the short-link or unstudded chain. (As to mode of making chain cables, see under CHAINS.) The cables for use in the mercantile service are made in 15 fathom lengths, but in government contracts chain cables are required to be made in $12\backslash frac\{1\}\{2\}$ fathom lengths, with one swivel in the middle of every alternate length, and one joining-shackle in each length. Besides the ordinary links and joining-shackles, there are end-links, splicing-tails, mooring-swivels, and bending-swivels. The sizes of chain cables are denoted by the thickness of the rod-iron selected for the links. The following table gives certain ascertained quantities concerning the cables in ordinary use:

Compared with the strength of hempen cable, 1 in. diameter chain cable is equivalent to $10\backslash frac\{1\}\{2\}$ in. circumference hemp, $1\backslash frac\{1\}\{2\}$ in. to $13\backslash frac\{1\}\{2\}$ in., $1\backslash frac\{1\}\{2\}$ in. to 16 in., $1\backslash frac\{1\}\{2\}$ in. to 18 in., and 2 in. to 24 in.

By the Chain Cables Act of 1871, certain bodies are licensed to erect machines for testing all chain cables and anchors; and it is forbidden to sell or purchase, under a penalty of £50, any chain cable or any anchor weighing more than 168 lb. which has not been duly tested. Minor alterations were introduced by a later Act (1874), leaving the main rules intact. For submarine cables, see TELEGRAPH; and for cable tramways, TRAMWAY.