Page:Encyclopædia Britannica, Ninth Edition, v. 7.djvu/820

796 ELAND (fioselaphus oreas) is the largest and most valuable member of the antelope family. It is fully equal to the horse in size, standing six feet high at the shoulders, nnd measuring nine feet from the nose to the root of the tail. In robustness of build it resembles the ox, and forms the type of the bovine subdivision of antelopes. Its neck is thick, and is furnished with a prominent dewlap, fringed with long hair. Except on the ridge of the back the fur is short, and is usually of a reddish fawn colour above and white beneath. Its horns are about 20 inches in length, nearly straight, and in the male are surrounded throughout the greater part of their length with a spiral wreath ; in the female they are more slender, and the spiral ridge is indistinct or absent. The eland is a native of South Africa, where it roams in considerable herds over the open plains, &quot; rejoicing,&quot; says a recent traveller, &quot; in the belts of shaded hillocks, and in the isolated groves of Acacia capensis, which, like islands in the ocean, are scattered over many of the stony and gravelly plains of the interior.&quot; It is slow in its movements as compared with the other antelopes, and is readily captured, while in disposition it is exceedingly gentle, and thus seems eminently adapted for domestication. It breeds readily in confinement, and herds of elands have already been introduced into various parks in Britain. Its flesh is highly prized as an article of food, resembling beef, it is said, iu grain and colour, but being more delicate and better flavoured. The eland is remarkable for the quantity of fat which it takes on, exceeding in this respect all other large game. The carcase of a single individual weighs from 1500 to 2000 R)s. The eland was formerly abundant in the neighbourhood of Cape Town, but is now rarely found within the colony, and should man not succeed meanwhile in domesticating it, there is reason to fear that a valuable source of animal food will be lost to him by the speedy extermination of the eland.  EL-ARAISH,, or in French, a town of Morocco en the Atlantic coast, about 45 miles S. of Tangier, is picturesquely situated on a rocky height to the south of the embouclmre of the Wady Loukhus or Lixus. It is the seat of a military governor, and has a number of well-kept though practically useless defences. The impress of Spanish occupation is still evident, and all the main points described in the 17th century by Pidon de Saint Olon can easily be distinguished such as the church, the fort of St Jacques, the castle of St Etienne with its four cupolas, the Jew s Tower, and the castle of Notre Dama d Europe, now the Kasba or citadel. The market-place is surrounded with arcades of monolithic sandstone pillars. In spite of the bar at the entrance of the river preventing the passage of all vessels of more than 1 50 tons, the port is one of the most frequented on that part of the coast. The exports, gradually increasing in value, consist mainly of millet, dra,and other cereals, canary-seed, beans, pease, cork, and wool. In 1875, 136 vessels entered and cleared, 26 being British and 58 Spanish. The population of the town at the same date was estimated at 5000, of whom nearly 4000 were Mahometans, about 1000 Spanish-speaking Jews, and 60 Christians.

1em 1em         LASTICITY of matter is that property in virtue of which a body requires force to change its bulk or shape, and requires a continued application of the force to maintain the change, and springs back when the force is removed, and, if left at rest without the force, does not remain at rest except in its previous bulk and shape. The elasticity is said to be perfect when the body always requires the same force to keep it at rest in the same bulk and shape and at the same temperature through whatever variations of bulk, shape, and temperature it be brought. A body is said to possess some degree of elasticity if it requires any force to keep it in any particular bulk or shape. It is convenient to discuss elasticity of bulk and elasticity of shape sometimes separately and sometimes jointly.

2. Every body has some degree of elasticity of bulk. If a body possesses any degree of elasticity of shape it is called a solid; if it possesses no degree of elasticity of shape it is called a fluid.

3. All fluids possess elasticity of bulk to perfection. Probably so do all homogeneous solids, such as crystals and glasses. It is not probable that any degree of fluid pressure (or pressure acting equally in all directions) on a piece of common glass, or rock crystal, or of diamond, or on a crystal of bismuth, or of copper, or of lead, or of silver, would make it denser after the pressure is removed, or put it into a condition in which at any particular intermediate pressure it would be denser than it was at that pressure before the application of the extreme pressure. Malleable metals and alloys, on the other hand, may have their densities considerably increased and diminished by hammering and by mere traction. By compression between the dies used in coining, the density of gold may be raised from 19 258 to 19 367, and the density of copper from 8 535 to 8 916 j and Mr M Farlane s experiments quoted below (section 78), show a piece of copper wire decreasing in density from 8 91 to 8 835 after successive simple tractions, by which its length was increased from 287 csntimetres to 317 centimetres, while its modulus of rigidity decreased from 443 to 420 million grammes per square centimetre. Later experiments, recently made for this article by the same experimenter, have shown augmen tation of density from 8 85 to 8 95, produced by successive tractions which elongated a piece of copper wire from weighing 16 4 grammes per metre to weighing 13 5 grammes per metre, the wire having been first annealed by heating it to redness in sand, and allowing it to cool slowly. Augmentation of density by traction is a some what surprising result, but not altogether so when we con sider that the wire had been reduced to an abnormally small density by the previous thermal treatment (the &quot; annealing&quot;). The common explanation of these changes of density in metals, which attributes them to porosity, is probably true ; by porosity being understood a porous structure with such vast numbers of the ultimate molecules in the portions of the solid substance between pores or interstices that these portions may be called homogeneous in the sense that a crystal or a liquid can be called homogeneous (compare section 40 below).