Page:The American Cyclopædia (1879) Volume VI.djvu/500

 492 ELATERIUM ELBA ceding table from Regnault has shown the connection between temperature and elastic pressure for some of the more interesting va- pors. For short distances on either side of the boiling point of a liquid the elasticity of its vapor approximately varies directly as the tem- perature, as was first propounded by Dalton. In considering the effects of heat on the elasti- city of a vapor or a gas, it is necessary to distin- guish between (1) the elastic pressure exerted by a gas that is confined within a constant vol- ume and has its temperature altered by exter- nal heat, and (2) the pressure exerted by a gas that is compressed by external force to a smaller volume, but whose temperature is not altered. The former is the elasticity under constant volume or the expansion under constant pres- sure ; the latter is the elasticity under constant temperature, and is for perfect gases expressed by Boyle's law, which however holds good only approximately for vapors. Gay-Lussac has shown that the expansion under constant pressure is sensibly the same for all perfect gases, and is such that the volume increases by 0-002036 of its original value for an increase of 1 F., or by 0-00367 for an increase of 1 0. This law was fully confirmed by Regnault, who showed that it is only approximately true when gases or vapors approach the point of lique- faction. The effect of heat on the elasticity of a gas is so combined with its effect on the density as in general to increase the velocity of the transmission of sound. Thus in air at a pressure of 30 inches the velocity in feet per second is 1,089 at a temperature of 32 F., but is 1,131 at a temperature of TO F. ELATERIUM (Gr. Mabveiv, to drive out), a sub- stance deposited by the juice of the fruit of momordica elaterium, or squirting cucumber, a plant of the order cucurbitacece, growing in the south of Europe. (See CTTOUMBEB.) It is found in thin flat cakes of a gray or greenish color, which have a feeble odor and a slightly bitter taste. Its medicinal activity depends upon a crystalline, neutral, active principle, called elaterine. This is insoluble in water and alkaline solutions, sparingly soluble in di- lute acids, and freely soluble in alcohol. The proportion of elaterine in different specimens of elaterium varies exceedingly, and the medi- cinal activity of the latter article varies pro- portionally. Elaterium and its active princi- ple elaterine are violent cathartics, and also increase somewhat the secretion of urine. In small doses, that is, from -fa to ^ of a grain of elaterine and from ^ of a grain to 2 grains of elaterium, these articles produce copious watery discharges, which are frequently at- tended with nausea, vomiting, and depres- sion. In larger doses they act with great vio- lence upon the stomach and bowels, and in still larger doses excite an inflammation of these organs which has sometimes proved fatal. Their action is rapid. They generally purge in an hour or less, and a legitimate dose may be repeated in an hour if it has not acted by that tune. On* account of the energy of their operation, they are not much used medicinally except when, in the treatment of dropsy and disease of the kidneys, it is desirable to obtain copious, frequent, and watery evacuation. They should always be administered cautious- ly, and never given when great constitutional weakness exists. ELiTH (in Josephus ^ffilane, in Roman geog- raphy Elane, now Ailah), a seaport of ancient Idumsea, on the shore of the eastern or Elanitic gulf of the Red sea, now the gulf of Akabah. It was a part of David's conquest from the Edomites ; was a place of great importance in Solomon's time, as the port in which he built and fitted out his ships for bringing gold from Ophir; was captured by the revolted Edom- ites in the reign of Joram, after having been in the possession of the Israelites 150 years; was retaken by Uzziah, who fortified it anew, peo- pled it with his own subjects, and restored the trade to Ophir ; was afterward taken by Resin, king of Damascus, who in turn was de- prived of it by Tiglath-pileser, king of Assyria, from whose time it was never recovered by the Jews. Later it fell under the power of the Romans, became the residence of a Chris- tian bishop, and submitted to the Moslems, its governor paying them an annual tribute. In 1116 it was taken by King Baldwin of Jerusa- lem, and in 1067 was again wrested from the Christians by Saladin. Edrisi describes it as a small town frequented by Arabs, and forming an important point on the route between Cairo and Medina. Elath adjoined Eziongeber; and Akabah now occupies the site of one or both of these ancient towns. ELBA, an island in the Mediterranean, belong- ing to the Italian province of Livorno, sepa- rated from the mainland by the strait of Piom- bino; length about 18 m., greatest breadth 12 m. ; area, about 90 sq. m. ; pop. about 20,000. Its outline is irregular, the mountains which traverse the island rising in some parts more than 3,000 ft., and being indented by deep gulfs and inlets, so that its breadth in some places does not exceed 3 m. The soil is fertile, but only a small portion is under tillage. The valleys abound with fruit trees, but are not well cultivated, and the fruits are of inferior quality, excepting oranges. Among the an- nual products of the island and its waters are red and white wine, marine salt, tunnies, sardines, anchovies, and other fish, and iron, for which the island has always been cele- brated. The iron is found in a mountain near Rio, on the E. coast, about 2 m. in circumference, 500 ft. high, and yielding from 50 to 75 per cent, pure metal. There are quarries of granite in the S. "W. part of the island, in which crystals of red and green tour- maline and emeralds are found. The princi- pal towns are Porto Ferrajo, Porto Longone, Rio, and Marciana. The island was called ^Ethalia by the Greeks and Ilva by the Romans, and was noted for its minerals. Ancient ruins