TONGA, or FRIENDLY ISLANDS 430 TONNAGE Wesleyan Methodists succeeded in the work of evangelization, and their labors were finally crowned with such success that most of the inhabitants are now Christians. Nearly all the islands are under the rule of one Christian chief; but by an agreement made between Eng- land, Germany, and the United States in 1899 the islands are under the protec- torate of Great Britain, Total area 385 square miles. Pop. (1917) 23,766, Euro- peans 347. TONGUE, in human anatomy, a mus- cular organ in the mouth, covered with mucous membrane, the muscular struc- ture rendering it of use in mastication, deglutition, and the articulation of speech, while the mucous membrane, which is endowed with common and tac- tile sensibility, constitutes it the seat of the sense of taste. The tongue occupies the concavity of the arch of the lower jaw; its basal or hinder part is connected with the hyoid bone, while beneath it is attached by means of the genio-glossus muscle to the lower jaw. The tongue is marked along the middle for nearly its whole length by a slight furrow called the raphe, often terminating behind in a depression called the foramen ccecum, within which mucous glands open. The upper surface of the tongue in front of the foramen is covered with small eminences called papillae, some circum- vallate, others fungiform, and the rest filiform, the last being the most numer- ous. Behind these are numerous small racemose glands, called lingual glands. TONIC, in medicine, any remedy which improves the tone or vigor of the fibers of the stomach and bowels, or of the muscular fibers generally. Tonics may be said to be of two kinds, medical and non-medical. Medical tonics act chiefly in two ways: (1) Indirectly, by first influencing the stomach and increasing its digestive powers ; such being the effect of the vegetable bitters, the most im- portant of which are calumba, chamomile, cinchona bark, gentian, taraxacum, etc. (2) Directly, by passing into and exert- ing their influence through the blood; such being the case with the various preparations of iron, certain mineral acids, and salts. The non-medical tonics are open-air exercise, friction, cold in its various forms and applications, as the shower bath, sea bathing, etc. TONKING, or T0NQT7IN, since 1884 a French possession, is the N. E, portion of the Indo-Chinese peninsula, bordering on China. Area, 119,660 square miles; pop. 6,200,000. Europeans, 6,000. Capi- tal Hanoi, also of all French and Indo- China. The name has been used for various areas in this region. The main feature of the country is the Sang-koi or Red river (variously spelt Sang-koi, Sang-coi, etc), coming from Yunnan, and traversing the whole of Tonking length- wisej with a large delta. The chief produce is rice, silk, sugar, pepper, oil, cotton, tobacco, and fruits, with some copper and iron; and companies are now working coal and antimony mines at one or two places on the coast, especially near the chief port of Haiphong. Products valued at $10,000,000 annually. The French scheme of tapping: the resources of Yunnan by means of the Song-koi has proved impracticable, the navigation of the upper course being very difficult. TONNAGE, in regard to ships, a measure both of cubical capacity and of dead-weight carrying capability. The term, used by itself, may have reference severally to "builders' old measurement" tonnage (B. O. M.), "register" tonnage, "displacement" tonnage, "freight" ton- nage, etc., each of which expressions is more or less current in shipping circles. From very early times in the history of shipping a scale of one sort or other must have been employed to determine the relative capacity or carrying power of different vessels, and in point of fact the term "tonnage" in this connection can be traced back for at least 500 years. In Great Britain the first Act of Parliament dealing with the subject was passed in 1422, a second was introduced in 1694, and a third in 1720, but the application of these was limited to particular classes of ships, or those employed in particular trades. "Displacement" tonnage is by general consent regarded as the fairest measure for the tonnage of naval ships since they are designed to carry certain maximum weights and to float at certain load lines which are fixed with reference to the character of service. It has for many years been the official tonnage for the warships of France and other European nations, and since 1872 — prior to which date the B. 0. M. rule was the only one employed — the tonnage of British naval ships has been based on the displacement principle. The United States navy has also adopted displacement tonnage; in fact, it is all but universally employed. "Freight" tonnage, a system of meas- urement commonly employed in connec- tion with stowage by merchants and shipowners, although it has no legal capacity, is simply a measure of cubical capacity. A freight ton, or "unit of measurement cargo," simply means 40 cubic feet of space available for cargo, and is therefore two-fifths of a register ton.
