Page:EB1911 - Volume 15.djvu/301

Rh JARGOON, or (occasionally in old writings jargounce and jacounce), a name applied by modern mineralogists to those zircons which are fine enough to be cut as gem-stones, but are not of the red colour which characterizes the hyacinth or jacinth. The word is related to Arab zargun (zircon). Some of the finest jargoons are green, others brown and yellow, whilst some are colourless. The colourless jargoon may be obtained by heating certain coloured stones. When zircon is heated it sometimes changes in colour, or altogether loses it, and at the same time usually increases in density and brilliancy. The so-called Matura diamonds, formerly sent from Matara (or Matura), in Ceylon, were decolorized zircons. The zircon has strong refractive power, and its lustre is almost adamantine, but it lacks the fire of the diamond. The specific gravity of zircon is subject to considerable variation in different varieties; thus Sir A. H. Church found the sp. gr. of a fine leaf-green jargoon to be as low as 3.982, and that of a pure white jargoon as high as 4.705. Jargoon and tourmaline, when cut as gems, are sometimes mistaken for each other, but the sp. gr. is distinctive, since that of tourmaline is only 3 to 3.2. Moreover, in tourmaline the dichroism is strongly marked, whereas in jargoon it is remarkably feeble. The refractive indices of jargoon are much higher than those of tourmaline (see ).

 JARĪR IBN ʽATĪYYA UL-KHATFĪ (d. 728), Arabian poet, was born in the reign of the caliph ʽAli, was a member of the tribe Kulaib, a part of the Tamīm, and lived in Irak. Of his early life little is known, but he succeeded in winning the favour of Hajjāj, the governor of Irak (see ). Already famous for his verse, he became more widely known by his feud with Farazdaq and Akhtal. Later he went to Damascus and visited the court of Abdalmalik (ʽAbd ul-Malik) and that of his successor, Walīd. From neither of these did he receive a warm welcome. He was, however, more successful with Omar II., and was the only poet received by the pious caliph.

His verse, which, like that of his contemporaries, is largely satire and eulogy, was published in 2 vols. (Cairo, 1896).

JARKENT, a town of Russian Central Asia, in the province of Semiryechensk, 70 m. W.N.W. of Kulja and near to the Ili river. Pop. (1897), 16,372.

 JARNAC, a town of western France in the department of Charente, on the right bank of the river Charente, and on the railway 23 m. W. of Angoulême, between that city and Cognac. Pop. (1906), 4493. The town is well built; and an avenue, planted with poplar trees, leads to a handsome suspension bridge. The church contains an interesting ogival crypt. There are communal colleges for both sexes. Brandy, wine and wine-casks are made in the town. Jarnac was in 1569 the scene of a battle in which the Catholics defeated the Protestants. A pyramid marks the spot where Louis, Prince de Condé, one of the Protestant generals, was slain. Jarnac gave its name to an old French family, of which the best known member is Gui Chabot, comte de Jarnac (d. c. 1575), whose lucky backstroke in his famous duel with Châteigneraie gave rise to the proverbial phrase coup de jarnac, signifying an unexpected blow.

 JARO, a town of the province of Iloílo, Panay, Philippine Islands, on the Jaro river, 2 m. N.W. of the town of Iloílo, the capital. Pop. (1903), 10,681. It lies on a plain in the midst of a rich agricultural district, has several fine residences, a cathedral, a curious three-tiered tower, a semi-weekly paper and a monthly periodical. Jaro was founded by the Spanish in 1584. From 1903 until February 1908 it was part of the town or municipality of Iloílo.

JAROSITE, a rare mineral species consisting of hydrous potassium and aluminium sulphate, and belonging to the group of isomorphous rhombohedral minerals enumerated below:—

Jarosite usually occurs as drusy incrustations of minute indistinct crystals with a yellowish-brown colour and brilliant lustre. Hardness 3; sp. gr. 3.15. The best specimens, consisting of crystalline crusts on limonite, are from the Jaroso ravine in the Sierra Almagrera, province of Almeria, Spain, from which locality the mineral receives its name. It has been also found, often in association with iron ores, at a few other localities. A variety occurring as concretionary or mulberry-like forms is known as moronolite (from Gr. , “mulberry,” and  , “stone”); it is found at Monroe in Orange county, New York. The recently discovered species natrojarosite and plumbojarosite occur as yellowish-brown glistening powders consisting wholly of minute crystals, and are from Nevada and New Mexico respectively.

 JARRAH WOOD (an adaptation of the native name Jerryhl), the product of a large tree (Eucalyptus marginata) found in south-western Australia, where it is said to cover an area of 14,000 sq. m. The trees grow straight in the stem to a great size, and yield squared timber up to 40 ft. length and 24 in. diameter. The wood is very hard, heavy (sp. gr. 1.010) and close-grained, with a mahogany-red colour, and sometimes sufficient “figure” to render it suitable for cabinet-makers’ use. The timber possesses several useful characteristics; and great expectations were at first formed as to its value for shipbuilding and general constructive purposes. These expectations have not, however, been realized, and the exclusive possession of the tree has not proved that source of wealth to western Australia which was at one time expected. Its greatest merit for shipbuilding and marine purposes is due to the fact that it resists, better than any other timber, the attacks of the Teredo navalis and other marine borers, and on land it is equally exempt, in tropical countries, from the ravages of white ants. When felled with the sap at its lowest point and well seasoned, the wood stands exposure in the air, earth or sea remarkably well, on which account it is in request for railway sleepers, telegraph poles and piles in the British colonies and India. The wood, however, frequently shows longitudinal blisters, or lacunae, filled with resin, the same as may be observed in spruce fir timber; and it is deficient in fibre, breaking with a short fracture under comparatively moderate pressure. It has been classed at Lloyds for ship-building purposes in line three, table A, of the registry rules.

 JARROW, a port and municipal borough in the Jarrow parliamentary division of Durham, England, on the right bank of the Tyne, 6 m. below Newcastle, and on a branch of the North-Eastern railway. Pop. (1901), 34,295. The parish church of St Paul was founded in 685, and retains portions of pre-Norman work. The central tower is Norman, and there are good Decorated and Perpendicular details in the body of the church. Close by are the scattered ruins of the monastery begun by the pious Biscop in 681, and consecrated with the church by Ceolfrid in 685. Within the walls of this monastery the Venerable Bede spent his life from childhood; and his body was at first buried within the church, whither, until it was removed under Edward the Confessor to Durham, it attracted many pilgrims. The town is wholly industrial, devoted to ship-building, chemical works, paper mills and the neighbouring collieries. It owes its development from a mere pit village very largely to the enterprise of (q.v.). Jarrow Slake, a river bay, 1 m. long by m. broad, contains the Tyne docks of the North-Eastern railway company. A great quantity of coal is shipped. Jarrow was incorporated in 1875, and the corporation consists of a mayor, 6 aldermen and 18 councillors. Area, 783 acres.

JARRY, NICOLAS, one of the best-known 17th century French calligraphers. He was born at Paris about 1620, and was officially employed by Louis XIV. His most famous work is the Guirlande de Julie (1641). He died some time before 1674.

JARVIS, JOHN WESLEY (1780–1840), American artist, nephew of the great John Wesley, was born at South Shields, England, and was taken to the United States at the age of five. He was one of the earliest American painters to give