CHAIN-CABLES are iron chains used in lieu of hemp cables for anchoring vessels. The liability of hemp cables to be destroyed by the alternate action of air and water, and especially by chafing in rocky anchorage ground, led M. Bougainville to suggest the idea of substituting iron as early as 1771 ; but the idea was not taken up till 1808, when Mr. Slater, a surgeon in the navy, obtained a patent for a chain-cable. Even after this many years elapsed before their advantages wree generally recognised. Chain cables are usually furnished with bolts at the distance of one or two fathoms from-each other, by with drawing one of which a ship may slip her anchor in case of emergency in less time hen would be required to cut a hemp cable. The weight of a chain-cable is an advantage while the ship is at anchor, as the strain is ncerted on the cable rather than on the ship, and must be excessive before it can draw the ?able straight.
Mr. Frearson, of Birmingham, patented in L848 a method of making chains (for cables and other purposes). The rod of iron is ;rasped while red•hot by tongs or pinchers, and drawn between two grooved rollers ; these rollers have so peculiar a movement imparted to them by machinery, that the bar is forced round a die or mandril, into a form fitted to produce a link ; while arrangements are at the same time made for connecting this link with the one lust made.
A new cable-piecing machine was intro duced in 1848 by Messrs. Dunn and Elliot, of Manchester. It consists mainly of a hori zontal iron cylinder, with a piston working to and fro. The chain-cable is attached to one end of the piston-rod ; and beyond this rod is a long iron trough, in a right line with the cylinder, and continuing to a considerable length, depending on the length of chain to he tested at one time. At the remote end of this trough a pair of claws grasp the other end of the chain; so that the chain extends from the piston to the claws, through the cylinders and the trough ; and any force which tends to move the piston backwards will stretch the chain. The end of the cylinder next the trough is made watertight ; and water is forced by a double hydraulic pump into the hollow space between the piston and this closed end of the cylinder : the cylinder is thus forced backward, and the chain becomes severely stretched. A water ram and scale beam are so placed in connection with the cylinder as to measure the amount of force exerted on the chain. Tho same machine can test strengths between the wide limits of i cwt. and 100 tons.
CHAl N-SHOT. Two iron balls linked together by a chain eight or ten inches long aro so called. They are used in naval ac tions.