Page:Encyclopædia Britannica, Ninth Edition, v. 5.djvu/189

Rh of the melting of the snows passes into these channels, and tends to keep them open ; so that when the inundation is over, the sea again flows into them. But along the inter vening part of the coast, the channels, like the intervening hillocks, are not continuous, but form chains of little lakes, separated by sandy isthmuses. Although these channels run nearly parallel to each other, yet they have a some what fan-like arrangement ; their centre of radiation being the higher part of the isthmus which separates the basin of the Caspian from the north-east portion of the Black Sea, a fact, as will be seen hereafter, of no small significance. The coast-line of the Bay of Mertvy Kultuk, on the other hand, is formed by a chain of low calcareous hills, con stituting the rampart of the plateau of Ust Urt or Turkoman Isthmus, which divides the Caspian from the Sea of Aral ; and it is between head-lands of this high plain that the long extension of this bay termed the Karasu (or Black Water) runs inland, the town of Novo Alexandrovsk being situated near its entrance. The northern basin of the Caspian may be considered to terminate on the west side with the Bay of Kuma, and on the east with the hilly peninsula of Mangishlak, on which the town of Novo Fetrovsk is situated. To the south of the line joining these points, in the parallel of 44 10 N. lat., the western shoreline is higher, and the water deepens considerably, thus forming the middle basin of the Caspian, which may be considered to extend as far south as Cape Apsheron, the south-eastern termina tion of the great Caucasian range. This middle basin receives the large river Terek, which discharges itself by several mouths (some of them entering the Bay of Kuma) through an alluvial delta ; and several smaller streams (low into it from the slopes of the Caucasian mountains through the low plain which intervenes between their base and the border of the Caspian. Near the most consider able of these, the Kabir Yalama, a rocky spur of the Caucasus comes down nearly to the sea ; and a narrow pass is thus formed, which has been fortified from very ancient times, being formerly known as the Albanice or Caspue Pylce, and now as the Pass of Derbcnd, this being a small town built on the declivity in which the range terminates. The eastern shore of this portion of the Caspian is formed by the plateau of Ust Urt, or &quot; high plain,&quot; a very remarkable plateau from 550 to 727 feet above the level of the Caspian, which extends from its eastern shore to the sea of Aral, rising .abruptly from I oth seas, and ranging about 400 miles in the north and south direction; its north and south borders are formed by a precipitous face or cliff, which has much the appearance of an ancient sea-margin. As it is composed of later Tertiary strata, its elevation must have occurred at a time not geologically remote. The headlands of the Ust Urt form an abrupt coast-line along the northern part of the eastern border of the middle basin, with occasional bays into which several small streams from the plateau discharge themselves. Further south, however, the plateau recedes, and the land shelves off more gradually ; and here an extensive but shallow basin presents itself (of which more will presently be said) almost entirely cut off from that of the Caspian, termed the Karaboghaz, or Black Gulf. To the south of this the coast-line rises again ; and a peninsula is formed by an extension of the Balkan Mountains, which may be considered as forming the southern termination of the middle basin. Except along the shore-lines, the depth of this basin everywhere excedes that of the northern, being greatest in its middle portion, where over a small area it reaches 400 fathoms, whilst it shallows again towards the south, where there is a sort of ridge between Cape Apsheron and the Balkan peninsula, at the average depth of 30 fathoms, that separates it from the southern basin. The soutliern basin ranges from the Balkan Peninsula on the east and Cape Apsheron on the west to the shore-line formed by the base of the great Elburz range of mountains, which curves round its low and swampy border, from the mouth of the Kur to Astrabad, at an average dis tance of about 40 miles, rising in the peak of Sawalan near Tabreez to 15,800 feet, and in the snow-capped summit of Demavend, on whose southern slope Teheran is situated, to 18,GOO feet. These mountains are composed of granite and porphyry, and are covered with recent volcanic deposits. South of Cape Apsheron, this basin receives the large river Kur, which drains the southern slopes of the Caucasian range ; and this is joined, at no great dis tance from its mouth, by another large river, the Aras or Arax (the ancient Araxes), which forms the boundary between Russian Trans-Caucasia and Persia. The joint channel discharges its water by several mouths, part of them opening into the Gulf of Kizil-Agatch, which is the most considerable extension of the southern basin. From the mouths of the Kur to the Gulf of Enzeli, which resembles the Karaboghaz on a smaller scale, there is no considerable stream ; but not far to the east of the town of Keshd of which Enzeli is the port, the Sefid or White River discharges itself, this being formed by the confluence of the Kizil-Uzen with another considerable river, the two together draining a large portion of the slopes of the western division of the Elburz range, and of its extension towards the Caucasus. The southern border of the Caspian, between the mouth of the Sefid and Astrabad, receives numerous small streams from the northern slopes of the Elburz, but no considerable river ; the Bay of Astrabad, however, receives at its northern end the Attruk, a river of considerable importance, which drains an extensive valley enclosed by the mountain ranges that form the southern border of the desert plains of Khiva. On the eastern coast, opposite to the Gulf of Kizil-Agatch, are the Balkan Bay and the Adji-Bojur Bay, which lie between extensions of the Balkan Mountains. One or both of these bays, it may now be pretty confidently stated, formerly received the mouths of the ancient Oxus (now Amou-Daria), when it discharged itself into the Caspian, instead of into the Sea of Aral ; and there is further reason to believe that a communication here at one time existed between the Caspian and the Sea of Aral, through a furrow which lies along the southern border of the Ust Urt, and which terminates in what was formerly known as the Gulf of Aboughir, a southern extension of Lake Aral now dried up. The depth of the southern basin of the Caspian is for the most part considerable, ranging in its central portion between 300 and 500 fathoms.

Drainage Area.—The drainage-area of the Caspian is much more extensive on the north and west than on the east and south. The Volga is estimated to drain an area of 527,500 square miles, and the Ural an area of 85,000 square miles, these two rivers together probably bringing down more water than the Danube and the Don pour into the Black Sea. When to these we add the Kuma, the Terek, the Arax and Kur, the Sefid, and the Attruk, it is obvious that the total amount of river water annually discharged into the basin of the Caspian must be almost, if not quite, the equal of that which is discharged into the basin of the Black Sea. Yet the whole amount of fresh water returned by rain and rivers to the basin of the Caspian is only sufficient to compensate for the lo?s by evaporation from its surface, as is shown by the fact that its present level remains constant, or, if it changes at all, rather sinks than rises. Now that the level of the Caspian was formerly about the same as that of the Black Sea, although at present 84 feet below it, is shown by the erosion of the rocks that formed the original sea-shore of 