left to protect Antioch, which was men- Tangential Force. In order to have a clear idea how the planets are made to revolve in consequence of the attraction which the sun, situated in one focus of their elliptical orbits, exercises upon them, we may imagine that they originally received an impulse urging them forward in a straight line. With this impulse the attraction of the sun (centripetal force; see Central Forces) being united, the planet was thus made to describe the diagonal of a parallelogram, whose sides represent the directions of these forces. As there is nothing to diminish the impulse which we have supposed originally given to the planet, it would continue its path in the direction of the diagonal; but the centripetal force, operating continually upon the direction which the planet has obtained, makes it change its direction incessantly. In this way originates (as a diagram, drawn according to what we have said, clearly shows) a motion around the centre of forces. (See Circular Motion, and Central Forces.) The planet has at each point of its path a certain tendency (the consequence of its previous motion; hence, properly speaking, the effect of its inertness) to continue its last received diagonal direction, and thus to recede from the centre of forces. To this tendency, the centripetal force, directed towards this point, is opposed. The centripetal force may again be divided into two forces, the first of which (the normal force) operates perpendicularly to the orbit, and only contributes to retain the planet in the same, in order to prevent the curved motion from degenerating into a straight one: the latter, however, coincides with the direction of the orbit tself, and, therefore, only affects the velocity. This latter force is the tangential force, so called because the element of the curve coincides with the tangent. The doctrine of central forces is so important, because our imagination, unaided by theory, is almost incapable of conceiving a body which turns around another, exercising an attraction upon it, yet without ever coming in contact with the attracting body. But what has been said shows that a correct proportion of the centripetal force to the original impulse renders the contact of the body with the sun impossible. Generally, the endeavor of the planet to recede from the centre of forces, is called the centrifugal force; but can we, properly, call that a force which is evidently the effect of inertness? The original impulse may be compared to the first impulse which sets the pendulum in motion; after which, if we omit other influences, it would continue its oscillations for eternity, from the mere influence of gravity. TANGIER, or TANJAH (anciently Tingis); a town of Morocco, situated at the west entrance of the straits of Gibraltar, thirty-eight miles south-west of Gibraltar; lon. 5° 50′ W.; lat. 35° 48′ N. The population is about 7000. Tangier was possessed by the English from 1662 to 1784. It afterwards became a distinguished station for piracy; but the disuse of this practice in Morocco has diminished the importance of the town. It now subsists chiefly by supplying the British garrison of Gibraltar with cattle and vegetables. The bay of Tangier is not safe when the wind is in the west, having been encumbered by the ruins of the mole and fortification; the cables are liable to be torn, and the ships to be driven on shore. Tangier, viewed from the sea, presents a pretty regular aspect; but within it exhibits the most disgusting wretchedness. It is the residence of the European and American consuls. TANNIN; a peculiar vegetable principle, so named because it is the effective agent in the conversion of skin into leather. The oak and its products-gall-nuts, &c.-contain two kindred matters, tannin and gallic acid, which seem, by the powers of vegetation, mutually convertible. The former is supposed to be characterized by its forming, with gelatine, a flexible and unputrefiable compound; and by forming with oxide of iron a black combination, which, having a strong affinity for cotton, linen, silk and wool, is much used by the dyer. Hitherto, tannin has been found only in perennial plants, and chiefly in the more durable parts of these. The barks of almost all trees and shrubs contain it, principally in the parts nearest the wood, because in the outer coats it is changed by the air. It has never been met with in the poisonous plants, nor in such as contain elastic, resinous and milky juices. Decoction of nutgalls contains tannin with a little gallic acid, some tannates and gallates of potash and lime, tannin altered into the matter commonly called extractive, and lastly a compound (insoluble in cold water) of tannin with perhaps some pectic acid, which is found especially in the extract of oak bark. The purification of tannin, or its separation from the principles with which it occurs, may be effected as follows:-Mix a filter- Proportion of Tannin in different vegetable Products. The most important property of tannin, among those above mentioned, is that displayed in its relation to animal gelatine. They combine with much facility, forming, from a state of solution, a soft, flocculent precipitate, which, on drying, becomes hard and brittle: this has been called tanno-gelatine. The combination is not always established in the same proportions, but varies according to the concentration of the solutions and the relative quantities of the substances; nor is the compound in all cases insoluble in water. When the gelatine is only slightly in excess, it consists of 54 gelatine and 46 tannin: when there is a large excess of gelatine, the compound is redissolved. On the formation of this combination, the art of tanning depends. The skin of an animal, when freed from the hair, epidermis and cellular fibre (which is done principally by the action of lime), consists chiefly of indurated gelatine. By immersion in the tan liquor, which is an infusion of bark, the combination of the tannin with the organized gelatine, which forms the animal fibre, is slowly established; and the compound of tannin and gelatine not being soluble in water, and not 108 1899900 36 16 6 liable to putrefaction, the skin is rendered dense and impermeable, and not subject to the spontaneous change which it would otherwise soon undergo. To render it equal throughout the whole substance of the skin, the action of the tan liquor must be gradual; and hence the tanning is performed by successive immersions of the skin in liquors of different strength. Sir H. Davy observes, that leather, slowly tanned in weak infusions of bark, appears to be better in quality, being both softer and stronger than when tanned by dense infusions; and he ascribes this to the extractive matter which they imbibe. This principle, therefore, affects the quality of the material employed in tanning; and galls, which contain a great deal of tannin, make a hard leather, and liable to crack, from their deficiency of extractive matter. Hides increase in weight during the process of tanning from one fifth to one third. TANNING is a mechanical art, by which the hides and skins of various animals, particularly those of neat cattle, are converted into sole leather, upper leather, harness, &c., by being cleansed of the hair and flesh, and saturated with the The tannin contained in the bark of the oak, hemlock, and some other kinds of forest trees. It is a simple process to make leather of hides and bark, but probably one of the most critical of manufacturing operations to make the most and the best leather that can be made from a given quantity of hide. The process is long and laborious. Time and labor are both materially reduced, and the quantity and weight of the leather increased, by various improvements, which commenced in the year 1803, in Hampshire county, in Massachusetts. improvements above alluded to are the substitution of water power for manual labor, in many of the most laborious parts of the process; viz. to soften and cleanse the hide preparatory to the bark being applied to it; to grind the bark; to move pumps for transferring the decoction of the bark from one vat to another (much of which is necessary to be done daily in an extensive tannery), and to roll the leather preparatory to its being sent to market; also the least possible quantity of lime is now used to facilitate getting off the hair: this has been found greatly to add to the weight and quality of the leather. The application of heat to bark in leaches is found to be very important, and more particularly the application of the decoction (usually termed liquor) to the hide, rather than the bark, which had been commonly employed. In 1829, 36,360 sides of sole leather were tanned in one establishment in the town of Hunter, Greene county, New York. They weighed 637,413 pounds, and were manufactured with the labor of forty-nine hands, and with 3200 cords of bark. The tannery has seven powerful water-wheels adapted to its various machinery. Slaughter hides averaged fifty-six and a half pounds of sole leather from one hundred of hide best South American dry hides gained sixty-one per cent. in weight, and ordinary ones in proportion.Tanning is a chemical process; and undoubtedly the art will go on improving with the progress of chemical science and the diffusion of chemical knowledge. TANSY (tanacetum vulgare). This plant is now naturalized, and pretty common in many parts of the U. States. It grows in beds by road sides, and in waste places. The stems are upright, branching, and about two feet high; the leaves doubly pinnate, and incisely serrate, and of an agreeable aspect. It belongs to the composite. The flowers are yellow buttons, disposed in a large, upright corymb. The whole plant has a strong and penetrating odor, agreeable to some persons, and an extremely bitter taste. It contains an acrid volatile oil, is stimulant and carminative, and the decoction and seeds are recommended as anthelmintic and sudorific. The young leaves are shredded down, and employed to give color and flavor to puddings; they are also used in omelets and cakes, and those of the curled variety for garnishing. TANTALITE. (See Columbite.) TANTALUS, son of Jupiter, and king of Sipylus, in Phrygia, was a favorite of the gods, who often visited him, until he forfeited their favor by his arrogance. Tradition does not agree as to his crime. According to one account, he offended Jupiter by his perfidy; according to another, he stole away the nectar and ambrosia from heaven; and a third story is, that he murdered his own son Pelops, and served him up for some of the gods. The same diversity prevails in regard to his punishment. He is sometimes described as having a large stone suspended over his head, which constantly threatens to fall and crush him, and from which he cannot flee. But the more common account represents him as standing up to his throat in water, with the most delicious fruits hanging over his head, which, when he attempts to quench his burning thirst or to appease his raging hunger, elude his grasp. From this fable comes the English expression to tantalize. TAPESTRY; a kind of woven hangings of wool and silk, frequently raised and enriched with gold and silver, representing figures of men, animals, landscapes, historical subjects, &c. This species of curtain-covering for walls was known among the inhabitants of Eastern countries at an extremely remote era. The most grotesque compositions and fantastic combinations were commonly selected for the display of the talents of workmen in this department of Oriental art, which was afterwards imported into Greece. From these compositions the elegant Greeks are supposed, by Böttiger, to have taken their ideas of griffins, centaurs, &c. At length the refined taste of Athens became visible in the structure of tapestries. The old grotesque combinations no longer, as formerly, covered their surfaces, but were confined to the borders only; and the centre received more regular and systematic representations. In modern times, this description of embroidery has been executed with very great success, and has often employed the talents of the greatest masters in the art of painting. In Flanders, particularly at Arras (whence the term arras, signifying tapestry), during the fifteenth and sixteenth centuries, the art was practised with uncommon skill; and tapestries were executed there after the masterly designs of Raffaelle in his cartoons. (q. v.) This art was introduced into England by William Sheldon, near the end of Henry VIII's reign. In 1619, a manufacture was established at Mortlake, in Surrey, by sir Fras. Crane, who received £2000 from James I, to encourage the design. The first manufacture of tapestry at Paris was set up under Henry IV, in 1606 or 1607, by several artists whom that monarch invited from Flanders. But the most celebrated of all the European tapestry manufactures was that of the Gobelins, (q.v.), instituted under Louis XIV, which sent forth very beautiful cloths, remarkable for strength, for elegance of design, and happy choice of colors. The finest paintings were copied, and eminent painters employed in making designs. For a long while Gobelin tapestry was the most costly and favorite method of hanging the walls of chambers. The texture of tapestry is in many respects similar to that of the finer carpetings; but the minuteness of the constituent parts causes the sight of the texture to be lost in the general effect of the piece. (See Carpets, and Hautelisse.) TAPEWORM, one of the most stubborn worms which infest the bowels of beasts, and also of man, has its name from the broad, flat, ribbon-like appearance of each articulation and of the whole body, which is composed of these articulations. Bremser makes two species-tania and bothryocephalus both of which were formerly united in one species, under the name of tania. One kind of both species appears in the human body; namely, 1. tania solium, the single or longlimbed chainworm, in which the organs of generation are found on one side of every articulation; it is the kind most commonly met with in Germany, France and England; 2. bothryocephalus latus, the proper or broad tapeworm, in which the sexual organs are found on the flat side of the articulations. It is met with only in Russia, Poland, Switzerland, and some parts of France, and causes little pain. Both kinds often reach the length of twenty or thirty feet, and usually only detached parts pass from the body, but not that which has the head; before this has passed away, the worm reproduces itself, and, moreover, what was formerly doubted, several tapeworms are often met with in one intestinal canal. The symptoms of the tapeworm are a peculiar, sudden sensation of pricking in the stomach, oppression, and undulatory motions in the abdomen, anxiety, cramps, swoons, &c.; but all these symptoms are uncertain, and only the actual passing of pieces of the worm from the body is a certain proof of its existence. The cure is difficult, and requires an experienced physician. TAPIOCA. (See Manioc.) TAPIR. The American tapir, when full grown, is six feet in total length, and about three and a half in height. In general form it resembles the hog; but the legs are rather longer in proportion, and the nose is prolonged into a small movable proboscis. The fore feet have four toes, and the hind ones three only. The eyes are small and lateral, and the ears long and pointed; the skin thick, and covered with scattering, short, silky hairs; the tail short, and slightly hairy. The teeth resemble those of the horse. It is the largest animal of South America, and is found in all parts of that continent, though most abundant in Guiana, Brazil and Paraguay. It shuns the habitations of men, and leads a solitary life in the interior of the forests, in moist situations, but selects for its abode a place somewhat elevated and dry. By travelling always the same rounds, it forms beaten paths, which are very conspicuous. It comes out only in the night, or during rainy weather, and resorts to the marshes. Its ordinary pace is a sort of trot; but it sometimes gallops, though awkwardly, and with the head down, and, besides, swims with facility. In the wild state, it lives on fruits and young branches of trees, but when domesticated, eats every kind of food. Though possessed of great strength, it makes use of it only for defence; and its disposition is mild and timid. The flesh is dry and disagreeably tasted; but the skin is very tough, and might be applied to useful purposes. The Indian tapir has only been discovered within a few years. It inhabits Sumatra, Malacca, and some of the surrounding countries. The colors are remarkable. The head, neck, feet and tail are black; the rest of the body and tip of the ears white. TAPROBANA (with the ancients); the name of Ceylon. TAR; a well known substance obtained chiefly from the pine by burning in a close, smothering heat. Some of the unctuous |