Table-lands, Plains and Deserts.— Tibet forms the most elevated table-land in Asia, its mean height being estimated at 15,000 feet. Its surface is very ringed, being intersected by a number of mountain ranges running generally in an easterly and westerly direction. On the east it is bounded by lofty mountains which separate it from China. Some of the largest rivers of southern and southeastern Asia have their origin in Tibet, including the Indus, the Brahmaputra, the Yang-tse and the Hoang-Ho. In this region. a numerous series of lakes run in a chain parallel to the Himalayas. Another great plateau, much lower, however, than that of Tibet, is the plateau of Iran, occupying a large portion of western Asia, extending from the Indus to the Mediterranean, and from the Persian Gulf to the Caspian Sea. It comprises the countries known as Afghanistan, Baluchis tan, Persia, Armenia and Asia Minor. It lies at altitudes varying from 2,000 to 8,000 feet above the sea. The eastern half of it consists to a large extent of unproductive wastes. Of great political and strategical importance at the junction of Turkestan, Afghanistan and India is the Pamir Plateau, already alluded to, called by the natives ethe roof of the Its val leys are at an elevation of from 11,000 to 13,000 feet above the sea. Another table-land of smaller extent and elevation is the Deccan Plateau, India, south of the parallel of lat. 25° N. The principal plain of Asia, as already men tioned, is that of Siberia, which extends along the north of the continent and forms a vast alluvial tract sloping to the Arctic Ocean, and traversed by large rivers, such as the Obi, the Yenisei and the Lena, that convey its drainage to that ocean. Vast swamps of peat-mosses called tundras cover large portions of this region. Southwest of Siberia, and stretching eastward from the Caspian to the Thian-Shan Mountains, is a low-lying tract, consisting to a great extent of steppes and deserts, and in cluding in its area the Sea of Aral, Bokhara, Khiva and other districts. This is a region of internal drainage, the rivers, among which are the Amu Darla and the Syr Dania, either falling into the Sea of Aral or into other smaller sheets of water. In the east of China there is an al luvial plain of some 200,000 square miles in ex tent, most of it productive and highly culti vated; in Hindustan there are plains extending for 2,000 miles along the south slope of the Himalayas; and between Arabia and Persia, watered by the Tigris and Euphrates, is the plain of Mesopotamia or Assyria, which could be made one of the richest in the world. Of the deserts of Asia the largest is that of Gobi, which is bounded on the north by the Yablonoi and Thian-Shan Mountains, on the south by Tibet, on the east by the Khingan Mountains on the borders of China; while in the west it extends into eastern Turkestan. Large portions of it are covered with nothing but sand or dis play a surface of bare rock. This desert forms a large part of the country known as Mongolia, the whole of which forms an area of internal drainage, deficient in rainfall. There are also extensive desert tracts in Persia, Arabia and Hindustan. An almost continuous desert region may be traced from the African desert through Arabia, Persia and Baluchistan to the Indus.
Rivers and Lakes.— Asia contains some of the largest rivers in the world. It is remark able among the continents for the number of its rivers, some of them of large size, that never find their way to the ocean, their waters either being lost in the sand or falling into lakes that have no outlet. The chief rivers in western Asia are the Tigris and Euphrates, that rise in the Armenian plateau and fall into the Persian Gulf ; the Indus, from the Tibetan plateau, flows through northwestern Hindustan and falls into the Arabian Sea; the Ganges, which rises in the Himalayas and flows eastward through northern Hindustan, and the Brahma putra, which rises in Tibet and flows through Assam and Bengal, both enter the Bay of Bengal; the Irrawaddy and the Salwen, rising in the mountains of the Indo-Chinese Peninsula, and both flowing through Burma, likewise en ter the Bay of Bengal; the Mekong or Cam bodia, the largest river of this peninsula, has its sources in the same mountains, and flowing southeastward enters the south China Sea; the Yang-tse and the Hoang-Ho, the two great rivers of China, rise in the Tibetan plateau; and enter the ocean . after a winding easterly course; the Amur, the only other great river of eastern Asia, rises in Mongolia, and after a cir cuitous course enters the Sea of Okhotsk; the great rivers of northern Asia, the Lena, Yenisei and Obi, have already been mentioned. The Yen
isei is believed to have a length of 3,400 miles, the Yang-tse of at least 3,000, the Lena of 2,770, the Hoang-Ho of 2,600. The basin of the Obi, including of course those of its tributaries, the Tobol and the Irtish, is believed to be the largest of any river in the world, except the Amazon and the Mississippi, being considerably over 1,000,000 square miles in area.
The largest lake of Asia is the Caspian Sea, which, however, is partly in Europe, its largest tributary being the Volga. The chief Asiatic rivers falling into this sea are the Kur from the Caucasus, the Aras from Armenia, and the Atrek from northern Persia — the river Ural being partly European, partly Asiatic. The Cas pian lies in the centre of a great depression, being 83 feet below the level of the Sea of Azof. East from the Caspian, as already men tioned, is the Sea of Aral, which, like the Cas pian, has no outlet, and is fed by the rivers Amu Dania and Syr Daria. Its area is esti mated at 27,000 square miles. Still farther east, to the north of the Thian-Shan Mountains, and fed by the Ili and other streams from this sys tem, is Lake Balkash, a somewhat crescent shaped sheet of water, with an area of 8,400 square miles. The lake has no outlet; its water is clear but very salt and disagreeable. There are also several other smaller lakes in this re gion, such as Issik-Kul, Kara-Kul, Ala-Kul, Baratala, etc. In the south of Siberia, between long. 104° and 110° E., is Lake Baikal, a moun tain lake from which the Yenisei draws a por tion of its waters; its area is estimated at about 12,500 square miles. In the very centre of the continent is the Lob Lake, or Lob Nor, to which all the drainage of eastern Turkestan converges, being conveyed to it by the Yarkand, Kashgar and other streams. These unite to form the Tarim River, which, from the source of the Yarkand, has a total length of over 1,200 miles. Lob seems to be rather a swampy tract than a lake proper. On the borders of Afghan istan, Persia and Baluchistan, is a similar swampy lake that receives the Helmund and other streams from Afghanistan. Of the nu merous lakes in Tibet Dangra-yum Nor and Tengri Nor seem to be the largest; the former is 45 miles long and 25 broad.
Geology.— Though in population and his tory the most ancient continent, geologically speaking Asia is considered, as regards its pres ent aspect, to be one of the newest. The prin cipal mountain chains are composed largely of granitic rocks. The Himalayan range of moun tains bears a striking resemblance in geological structure to the Alps; they are composed of granite gneiss and mica-schist, with syenite and amphibolites or trap-rocks, particularly primi tive greenstone; the Altai Mountains contain granite in layers without alteration of gneiss, argillaceous schist in contact with greenstone, and containing augite, jasper, calcareous rocks, argentiferous lead ore and copper. The rami fications of the Altai into Russian Asia contain also coal-grit, schists, quartz and greenstone, rich with lead, silver and auriferous sand. The lower ranges are covered with transported layers of rolled stones of granite, gneiss and porphyry, in which are found agates, carnelians and chalcedonies. In the Kuen-Lun group are found rubies, lapis-lazuli and turquoises. In the eastern part of the Urals the granite, of which the chain is composed, along with gneiss and other rocks, is extremely rich in iron and copper. The Caucasus contains granite, argil laceous schist, basaltic porphyry, petroleum and gold, which is also found in Siberia, northern India, Siam, Borneo and Tibet. Diamonds and other precious stones are also found in Borneo as well as in India and Ceylon. The coal fields of China are perhaps the largest in the world. The great plains of northern India, Mesopotamia, central Asia and Siberia are re garded as of very recent geological origin. From various indications many geologists are of opinion that the greater part of western Asia was occupied at no very distant period by an ocean, of which the Caspian and Aral Seas are the remains. It is also conjectured that a continental area extending across the Indian Ocean united Asia during the Permian period to Africa and Australia. Siberia is supposed to have been twice submerged during the Palm ozoic and the later Tertiary period. A line of volcanic action extends on the eastern coast from Kamchatka through the Philippines and the Malay Archipelago to Aracan in the Bay of Bengal. In Kamchatka there are eight or nine active volcanoes; in the interior of the con tinent there appear to be none at present active.