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The English system of measuring the tonnage of vessels in the eighteenth century is given in Falconer's Marine Dictionary, 1780, as follows:

"To determine the burden, or, in other words, the tonage, of a ship, it is usual to multiply the length of keel into the extreme breadth of the ship within board, taken along the midship beam, and multiplying the product by the depth in the hold from the plank joining to the keelson upwards to the main-deck, and divide the last product by 94; then will the quotient be the burden required, in tons."

This rule continued in force till 1819, when it was changed by the Lords Commissioners of the Admiralty as follows:

"Multiply the length of the keel by the breadth of beam, and that product by half the breadth of beam, and divide the last product by 94, and the quotient will be the tonnage" (Marine Dictionary, William Burney, LL.D., 1830). Dr. Burney remarks: "It appears from the general construction of merchant ships, that more attention is paid to evade the tax on tonnage than to their sailing well with the wind in different directions; and if the real tonnage of ships were taken, an alteration would soon be made in the construction for the better."

This form of the rule continued until 1842, when by Act of Parliament the following method was adopted:

"Divide the length of the upper deck between the after part of the stem and the fore part of the stern-post into six equal parts. Depths: at the foremost, the middle, and the aftermost of these points of division, measure in feet