CABLE. The rope or chain by which the anchor of a ship is held. Cables, un til within a recent period, were usually made of hemp, but of late years iron chains have come much into use. A hempen cable of 12 inches girth, and length 120 fathoms, weighs 3075 lbs. Since the weights of two cables of cqiial lengths will be as their sections, or squares of their girths, it is easy to de duce the following rule for the weight of any hempen cable :—Multiply the square of the girth in inches by 21.3 (or 21 near ly enough), the product is the weight in lbs. Since also as the breaking strain, or resistance against the force to part the cable, will be as the section, it will he as the weight, and will, be found nearly by dividing the weight in lbs. by 100: the quotient the breaking strain in tons. This rule is of course liable to great uncertainty from the quality or wear of the cable. Chain cables possess great advantages over hempen cables ; they are not liable to be destroyed by chafing on rocky grounds, nor to become rotten and insecure from alternate expo sure to the air and water ; and by reason of their greater weight the strain is ex erted on the cable rather than on the ship. In order that the ship may be en
abled to let slip her cable in case of neces sity, chain cables are furnished with bolts at distances from each other of a fathom or two, which can be readily with drawn. A chain of which_ the section is 1 inch in diameter breaks with 16 tons ; such a chain is equivalent to a 10 inch hemp cable nearly. And the dimensions of the chain cable corresponding to any hemp cable arc therefore easily found by merely dividing the circumference of the hemp cable by 10. The strength of every part of the chain is proved before it leaves the manufactory.