Tonnage

tun'naj, the carrying capacity of a ship. Wharf dues, canal tolls, pilot's fees, towage, etc., are based on the tonnage, that is, the size, not the weight, of the ship. One hundred cubic feet are considered a ton. In 1873 a congress held at Constantinople fixed rules for computing the tonnage of ships passing through the Suez Canal. Allowance is made for the space occupied by the engine room and screw shaft. Otherwise the capacity is determined by measurement of the total length and depth and average width. To this must be added storage capacity above the main deck. The total is the registered tonnage of the ship. It is made a matter of official record, so that it is not necessary to measure a ship every time the master pays canal or port dues. In ships contracting to carry freight by the ton, charges are based on the space occupied. Unless otherwise agreed, forty cubic feet of freight are reckoned a ton.

In railroad offices tonnage refers to the number of tons, by weight usually, of freight transported; in shipping circles tonnage has reference to cubic capacity only. The United States government levies a port duty of six cents a ton on transoceanic steamers coming into our ports. This tax is imposed upon the carrying capacity of a ship, and the ton, as spoken of in this connection, has no reference whatever to weight.

The gross tonnage of a ship includes the cubical contents of the entire closed parts of the ship--everything which is sheltered from the weather. The Lusitania, for instance, has a gross tonnage of 31,500--which is to say that her cubical contents, without any deductions, are 3,150,000 cubic feet.

The tonnage tax is computed upon the net tonnage, which represents the money-earning capacity of a ship. In reckoning the net tonnage of the Lusitania, deductions are made for the space taken by quarters for officers and crew, by the boilers and machinery, and by the coal bunkers. In the Lusitania these deductions amount to 71 per cent of the ship's cubical contents, and leave 913,500 cubic feet of capacity for cargo and passengers. Consequently the net tonnage of the Lusitania is 9,135.

When the Lusitania enters New York harbor she is charged six cents a ton on this net tonnage. The fee for a single entry is $548.10. The present law provides that the maximum charge for a single ship shall be the equivalent of fees for five entries, regardless of the number of calls made during the year. Accordingly, the Lusitania pays $2,740.50 each year to the United States government for the privilege of entering New York harbor. The six cent tonnage tax brought into the treasury $884,377 from 4,937 boats in the fiscal year ending in 1909.

According to Lloyd's Register for 1909-10 it appears that the ocean tonnage of the world amounts to 41,449,767 tons. Of this total 36,473,102 tons represent gross tonnage of steam vessels. In the following table all countries are included whose aggregate tonnage exceeds 100,000 tons: