9. Cargo measuring the cargo, two dif ferent kinds of tons may be used—the weight and the measurement ton. The weight ton again may be a "long," a "short," or a "metric" ton. As a rule the "long" ton of 2,240 pounds is used in ocean transpor tation, tho in European trade the metric ton is fre quently used. This ton of 1,000 kilograms equals 2,204.6 pounds avoirdupois. The "short" ton of 2,000 pounds is rarely used in shipping.
We have two things to reckon with in loading a ship : the weight which the ship can safely carry and the cubic capacity. The most economical cargo is that which completely fills the available space when the ship is down to its Plimsoll line or the American equivalent in depth. This is an ideal relation between weight and bulk which is not often afforded by any one article. A mixed cargo is, therefore, a generally desirable thing. What one kind of freight lacks in weight may be made up by another kind which has weight but little volume.
The ship owners have established a fixed ratio be tween the weight and the bulk of freight in the "measurement ton." This must not be confused with the "measurement ton" as applied to the vessel. The "measurement ton" as applied to the cargo equals 40 cubic feet. The ship's measurement ton is, there fore, equal to two and one half cargo tons. This unit of measurement is said to be based upon the fact that 40 cubic feet of wheat weigh one long ton. Freight rates are frequently quoted "at ship's option," mean ing that the company reserves the right to charge on the basis of weight or of measurement, choosing whichever yields the most favorable returns. In the parlance of the sea, some goods "weigh more than they measure," while others "measure more than they weigh." The former is called "deadweight" cargo ; the latter "measurement" cargo.
10. Official registration of vessels en gaged in foreign trade are registered by the gov ernment whose flag they fly. Registration also sig nifies that the machinery, the hull, crew's quarters, the life-saving equipment and other important parts of the ship have been officially inspected and ap proved. It definitely entitles the ship's claim to the benefits of all treaties and its country's protection.
Ships engaged in coastwise traffic are similarly in spected and registered, but the operation is called .c'enrolment." In the United States, registration and enrolment are administered by the Bureau of Navigation of the Department of Commerce. A list of all vessels of American registry is published by the Bureau under the title, "Annual List of Merchant Vessels of the United States." The first registry act of September 1, 1789, lim ited American registry to ships built in the United States. Many Americans, however, have invested in foreign-built ships. They found themselves em barrassed at the outbreak of the European War in being forced to fly foreign flags from their property. Accordingly, foreign-built ships certified by the Steamboat Inspection Service as safe to carry dry and perishable cargo are now admitted to American registry for foreign trade and trade with the Philip pines, Guam and Tutuila.
In Canada the Department of Marine and Fish eries publishes a yearly "List of Shipping" which is a list of vessels on the registry books of the Dominion of Canada.
11. Registry by private agencies.—In order to en able marine underwriters to judge the seaworthiness of a vessel seeking insurance, several private agencies furnish an inspection service, the best known being that of Lloyd's Register of British and Foreign Ship ping, which is not to be confused with the corpora tion of Lloyd's, the world center of marine insurance.
Lloyd's Register lists over 10,000 ships. In order to be classified the ship must satisfy strict rules. It must be constructed under supervision of a "Lloyd surveyor" (there are 360 such surveyors in the world's ports) and must submit to a survey every four years. Registration is not compulsory, but no ship owner can well afford to ignore "the Book," any more than a business man can afford to refuse to report to Dun or Bradstreet.
"The Book" contains all the salient particulars about each vessel listed, such as material of which it is constructed, code letter, name of the master, number of decks, tonnage, builder, port, engine, and rating. The rating is by the familiar "100 A 1," "95 A 1," etc.