TTRAL MOUNTAINS. 753 URANIUM RAYS. L'ral in the south, ami the Volga and Pctchoia on the west. The vegetation in the southern portion consists mainly of steppes with isolated oases of trees. The central portion is covered with immense forests of spruce, larch, and firs. which in the north give place to dwarf birch and mossy tundras. Geologically, the range consists of a central longitudinal zone of metamorphic slates, granites, gneisses, and syenites, flanked on either side by sedimentary strata, which are chiefly Carboniferous and Permian in the western, and Cretaceous and Jurassic in the eastern zone. In the southeast there are large Devonian outcrops and intrusions of quartz and porphyry. The Ural Mountains are extremely rich in minerals, which are chiefly confined to the central division, the northern parts being barren. There are ricli deposits of iron ore — magnetite, limonite, and red hematite. Nearly IY2 million tons of ore are produced annually and smelted into pig iron on the spot, the vast forests yielding an inexhausti- ble supply of fuel. Gold is mined both from veins and placers, and other rare metals, plati- num, iridium, and osmium, are comparatively abundant. The Urals yield 90 per cent, of all the platinum produced in the world. Precious stones are also mined, as well as copper, sil- ver, mercury, cobalt, nickel, and zinc. Coal beds exist on the western slope, but are not yet mined to any great extent. Asbestos is one of the distinctive mineral products of the moun- tains. This mineral wealth has given rise to im- portant industries, and a large number of popu- lous towns have sprung up among the mountains, while a considerable agricultural population has also been attracted. Consult : Ludwig, Veberblich der geologischen Beobachtunffcn (Leipzig, 1862) ; Hochstetter, Veber den'Vral im Ural (Berlin, 1873); Hie- kisch. Das System des Urals (Dorpat, 1882). URAXSK, 00-ral'y'sk. A territory of Rus- sia, lying mostly east of the Ural River, the boundary line between Europe and Asia (Map: Russia, H 5). Area, over 125,100 square miles. The surface generally presents a series of dry steppes and deserts sloping gradually to the Caspian. Much of the interior lies below the level of the Caspian. There are many salt lakes, and only the Ural (q.v.) and the Emba (during a part of the year) reach the Caspian, the other streams being lost in the lakes or in the sand. Uralsk is scantily watered, and there are places where even wells are lacking. The climate is continental, the influence of the Caspian Sea being confined to the coast region. The temperature is subject to wide fluctuations, and the precipitation is slight. In the winter the snowstorms are very destructive. Uralsk con- tains little cultivable land, and agriculture is of secondary importance, the chief occupations being stock-raising and fishing. The fisheries along the Ural and the coast of the Caspian Sea aro among the most extensive and the best regulated in Russia. The value of the fish, caviar, fish oil, and other fish products exported from the terri- tory exceeds $1,500,000. The population was 691,887 in 1901. Capital, Uralsk. URALSK. The capital of the Territory of Uralsk, in Southeastern Russia, at the confluence of the Ural with the Tchagan, 980 miles southeast of Moscow (Map: Russia, H 4). It is a well laid out town with an industrial school for Kirghizes and a natural history nmseum. It is the commercial centre of the province. Popula- tion, in 1897, 38,919. The town was founded at the lieginning of the seventeenth century. URA'NIA (Lat., from Gk. OiVai/a, Ourania, the Heavenly One, from ovpavdr, ouranos, heaven, sky ; connected with Skt. Varuna, Va- runa, god of the sky and waters, from var, to cover). One of the Muses (q.v.). In the later division of functions among the Muses, she be- came tlie guardian of Astronomy, or rather of the astronomical epic, such as was written by Aratus. She seems to be indicated in the groups of Muses by the globe. URANINITE. A mineral uranium oxide usuallj' found in the form of botryoidal or com- pact masses and often containing such im]uirities as silica and the oxides of iron, lead, calcium, and magnesium. It is opaque, grayish, greenisli, or brownish black in color, with a sub-metallic lustre, and has a conchoidal fracture. It occurs often w'ith ores of silver and lead, in Bohemia, Saxony, Hungary, Turkey, etc. See also Ra- dium ; Polonium ; Radioactivity. URANIUM (Xeo-Lat., named after the planet Uranus). A metallic element discovered by Klaproth in 1789. It is found chiefly as an oxide in the mineral uraninite or pitchblende, which occurs at various localities in Norway, Saxony, Cornwall, and the United ■ States, and also in various other minerals, but in smaller quantities. An important source of uranium compounds in recent years is the uran- ochre from Cornwall, England. The metal itself may be obtained by reducing uranous chloride by sodium or potassium in a crucible packed with charcoal, which is slowly heated to redness in a furnace. Uranium (symbol. U; atomic weight, 239.59) is a hard silvery-white metal with a specific grav- ity of 18.68. It melts at a bright red heat. It combines with oxygen to form a dioxide and a tri- oxide. which unite with bases to form uranous and uranic salts. Perhaps the most important of the salts is sodium uranate, known as uranium yellow, that is used for painting on glass and porcelain, as well as in making the fluorescent yellow 'uranium glass.' The two oxides combine to form a green uranoso-uranic oxide that is also formed when uranium is burned in the air. This oxide is used sometimes to produce a black glaze on porcelain. URANIUM RAYS. Certain radiations dis- covered by Professor Becquerel in 1890 to be emitted by the salts of uranium and the metal itself, and not to obey the laws of light or ether waves. This radiation has been shown by Ruther- ford to consist of two quite distinct groups of rays. Both aflfeet photographic plates, both ionize gases (see Ioniz.tion) , and both penetrate many bodies which are opaque to light : the two groups are distinguished by their ditTerent pene- trative powers, and consequent different ionizing powers. The more penetrating rays have less ionizing power and are deflected by a magnet and by an electrostatic field, much more than the other rays, but in an opposite direction. There are several other 'rudioactive' substances, as such bodies are called, which emit radiations like ura- nium: thorium and its salts, polonium, radium.
