Tonnage

Tonnage, a measure for determining the cubical capacity and carrying-power of ships and thus estimating the dues on shipping. The "register" ton now in use was enforced by the British Merchant Shipping Act of 1854, amended in 1862 and 1867, and has been adopted by various foreign countries. It is equivalent to 100 cubic feet of space, so that a vessel with an internal volume of 100,000 cubic feet is 1,000 tons register. The Act makes provision not only for ascertaining the depth of a ship in addition to its length and breadth, but for taking into account the curvature of the hull by means of cross measurements at various points. A deduction is made for crew-space, and on steamers for the engine-room, boilers, etc. On the other hand, the poop and other closed-in spaces above the upper deck available for stowage, are added to the "nett register" tonnage.