10 ASIA Menam, which traverses Siam; and the Me- kong, or Cambodia, which flows through Anam. These rivers traverse regions little known. 4. The Brahmapootra and the Gan- ges form a double system. The Brahmapoo- tra, according to the still doubtful assumption which makes the Dzang-botziu its upper course, rises in the lofty table land of Thibet, its head waters being not far from those of the Indus. After watering the long valley of Thibet, it makes a sudden bend to the south, cuts through the Himalaya chain near its E. end, and falls into the bay of Bengal, its waters near the mouth sometimes interlocking with those of the Ganges. The latter rises on the southern side of the Himalaya, and after run- ning S. E. through the plains of Bengal, and receiving in its course 12 large rivers, falls into the bay of Bengal. The Brahmapootra and the Ganges drain an area of about 500,000 sq. m., and there is scarcely a spot in Bengal more than 20 m. distant from one of their tributary streams, navigable even in the dry season. 6. The Indus rises near the head waters of the Dzang-botziu, but breaks through the Hima- layan chain toward the N. W. end, and after a course of 1,800 m. falls into the Arabian sea, on the opposite side of the peninsula of Hin- dostan. It drains about 350,000 sq. m. 6. The Euphrates and the Tigris, rising in the mountains of Armenia, flow for some distance close to each other, but after descending into the plain diverge to a distance of more than 100 m., again approach, and finally unite, falling into the Persian gulf under the name of the Shat-el-Arab. The region between them is the Mesopotamia of the ancients. The length of the Euphrates is about 1,800 m. ; that of the Tigris, which pursues a more direct course, about 1,150. The basin of the Euphrates and Tigris occupies about 250,000 sq. m. The lakes of Asia are of less importance than those of America or Africa. The Caspian and the Aral, however, commonly called seas, may more properly be regarded as lakes. The for- mer, 700 m. long and 200 broad, lies 83 ft. below the level of the Black sea. Although it receives the waters of the Volga, the largest river of Europe, it has no outlet, and its wa- ters are salt. The Aral, 300 m. long and at its centre 150 broad, lies about 40 ft. above the same level ; its waters are salt, but less so than those of the Caspian. It is probable that these two lakes were once united. Lake Bai- kal, in S. Siberia, has an area of about 13,000 sq. m., being, next after Superior, Michigan, and Huron, the largest body of fresh water on the globe, and lies about 1,400 ft. above the ocean level. Lake Balkash, or Tenghiz, 250 in. long and 70 broad, has an area of upward of 8,000 sq. m., approaching that of Erie. China has six considerable lakes, of which the two largest, Po-yang and Thung-thing, have each an area of about 3,000 sq. m., a third of that of Erie. The Tengrinoor in Thibet is of about the same dimensions. In Turkish Armenia is the great salt lake of Van. In Persia are the large salt lake of Urumiah, the small fresh-water lake of Hamun, and the little salt lake of Bakhtegan. Lake Asphaltites, or the Dead sea, in Palestine, is notable for its great depression and the exceeding saltness of its wa- ters. The proportion of Asia practically unin- habitable, either on account of extreme cold or the absence of water, is very great. A consid- erable part of Siberia lies north of the zone of cultivation. The great sand plain of Gobi, larger than France and England, is practically a desert. E. of the Caspian lies the large sandy desert of Khiva in Turkistan ; and a still larger one occupies the centre of Iran. The great peninsula of Arabia is mainly a desert, which stretches northward and includes a con- siderable part of the plain of the Euphrates, having altogether an area of nearly 1,000,000 sq. m. Between the plains of Hindostan and the left bank of the Indus lies the Indian des- ert, 400 m. broad. Probably fully a quarter of Asia may be considered a desert region. The climate of Asia embraces every general variety and every local incident : the rainless and riverless plains of Gobi, and the super- abundant moisture of the Indian seacoast ; the extremes of heat and cold in Siberia and the steppes; the more equable and agreeable cli- mate of Asia Minor ; gradations of temperature indicated both by a latitude ranging from the equator almost to the pole, and by a range of elevation from several hundred feet below the level of the sea to 29,000 feet above it. In no part of the earth's surface are the modifications of temperature, and consequently of products, more strongly marked ; while in some spots the inhabitants behold at one view in their valleys and hillsides the animal and vegetable life of the tropics, of the temperate, and of the frigid zone. The vast plains of Siberia are exposed to the extremes of temperature. In Tobolsk the thermometer for weeks during the summer remains at from 80 to 90, while the mean winter temperature is below zero. At Yakutsk the mean annual temperature is 13'43, while in the summer it rises to 80. The reason for this extreme variation is the distance of these plains from the ocean. The veil of mist which in more equable climates moderates the intensity of the rays of the summer sun is wanting ; while in the winter no breeze laden with moisture is present to temper the extreme cold natural to the high latitude. The prevalent winds are from the southwest. These reach eastern Siberia after having traversed wide stretches of land covered with ice and snow, and being thus deprived of their caloric and moisture, they become cold land winds. This applies to the whole of Asia N. of lat. 35. Compared with the maritime portions of Eu- rope, the difference is striking. In Peking, lat. 39 54', the mean annual temperature is 9 lower than at Naples, which lies a little to the north; and 4 -5 lower than at Copenha- gen, which is 17 nearer the pole. The rain-
