Caspian Sea (called by the Russians also the sea of Astrakhan; anc. Mare Caspium or Hyr-canum; Gr. Kapiria θaλaσσa), an inland sea, lying between Europe and Asia, between lat. 36° 30' and 47° 30' N., and lon. 46° 48' and 54° 25' E.; greatest length from N. to S., 760 m.; greatest breadth, 300 m.; average breadth about 200 m.; area, according to Berghaus, 156,800 sq. m. It is bounded N. W., N., and N. E. by Russia, S. and S. W. by Persia, and E. by Tur-kistan. It has few bays, the most important being, on the Asiatic side, Emba bay, Mertvoi gulf, Karasu inlet, Manghishlak gulf, bay of Alexander, Kenderlinsk gulf, Kara-Bugaz bay, and Balkan bay; on the European side, Kizil Agatch and Kuma gulfs, and several smaller indentations. At the S. extremity of the sea is Astrabad bay. The Emba river, which enters the bay of its own name by several mouths, and the Atrek, are almost the only considerable rivers which it receives on the E. side, though the Oxus, or Amoo, which now enters the sea of Aral, is supposed to have once flowed into it. On the N. and W. its basin is far more extensive.

The Ural, the Volga, the Kuma, the Terek, and the Kur here pour their waters into it, and most of them are constantly bringing accumulations of sand, which in some instances, as at the mouth of the Volga, form little islands, projecting several miles from the coast. All this part of the coast, as far S. as the Sulak, is of alluvial formation; thence S. to the peninsula of Apsheron it is of tertiary formation, broken by occasional carboniferous strata; and from Apsheron around the S. extremity of the sea, the shores are low and sandy, with lofty hills rising in the background. On the E. and S. E. is found a cretaceous subsoil, covered with moving sands; the surface, with the exception of Cape Karagan, being flat. In fact, the coast generally is so low that most parts are overflowed when the wind sets in strongly from the opposite quarter. Naphtha, or petroleum, is found in immense quantities, particularly in the vicinity of Baku on the peninsula of Apsheron and on the island of Naphthalia, in the bay of Balkan. There is a large export of petroleum to the Tartar and Persian ports on the S. and E. shores of the sea. In May, 1809, there was an extraordinary conflagration caused by the accidental ignition of large naphtha streams flowing on the surface of the sea.

The waters are not so salt as those of the ocean, owing to the immense volume of fresh water constantly poured in by the Volga and other large rivers. It is very deep, particularly on the S. shore, where a line of 450 fathoms will not reach bottom; but in the north and off the mouths of the Volga it is quite shallow, with frequent shoals. There are no tides, and the sea has no outlet, the superfluous waters being carried off wholly by evaporation. Extraor-dinarv changes in its level have been noticed, but never explained; according to native accounts, the surface rises and falls several feet in periods of about 30 years. It has long been known that the level of the Caspian is lower than that of the ocean, and in 1812 an attempt was made by Engelhardt and Parrot to ascer-tain the difference by a series of levellings and barometrical measurements across the Caucasian isthmus to the Black sea. Measurements were made in two places, one of which made the Caspian 348 ft. lower than the Black sea, and the other 301 ft. lower. A survey made by the Russian government in 1836-'7 proved the difference of level to be 84 ft.

Sturgeon, sterlets, balugas, salmon, and seals are taken in great numbers. - We know little of the ancient commerce of the Caspian. About the middle of the 13th century much of the trade of W. Europe with India passed over it, Astrakhan being then, as now, its chief port. On the seizure of Constantinople by the Turks commerce was forced into other channels. In 1560 an English company made a fruitless attempt to render it a channel of commerce with Persia and Turkistan. Peter the Great had its coasts explored by Dutch navigators, partly with the view of founding stations for the Indian trade on the Persian seaboard, but his project was not carried out. No Russian conquest was made on the Caspian sea until the time of Catharine II. and it was not till still more recent periods that Russia succeeded in obtaining full control over its trade, which is small, though constantly increasing. The largest class of vessels navigating the Caspian, carrying from 90 to 200 tons, are called schuyts, and are built of the timber of the boats that bring breadstuffs down the Volga to Astrakhan. Another class of vessels, of superior sailing qualities, carry from 70 to 140 tons, and are called raschips. Besides these, a great number of small craft are employed in coasting, fishing, and as lighters.

The Caspian steamboat navigation company was chartered in 1858, and steamboats are now common on the Volga and at all the important ports in the Caspian. Canals uniting the head waters of the Volga with Lake Ilmen and the Diina establish connections between the Caspian and the Baltic. The Russian government has projected a canal to connect the Caspian with the sea of Azov, and then with the Black sea, for which surveys were made in 1855, 1860, 1864, and 1871. The principal ports are Astrakhan and Baku, from which trade is carried on with Astrabad, Balfrush, and other Persian ports on the south, and with Manghishlak, Balkan, etc, on the east. Russia maintains a fleet on the Caspian, and has three fortified settlements on the E. coast. - Dureau-Delamalle's Geographie physique de la Mer Noire, Eich-wald's Reise auf dem Kaspischen Meere und in den Iiaukasiis, Hommaire de Hell's Les steppes de la Mer Caspienne, the Beschreibung published by Sawitsch and Sabler, giving their survey of the respective elevation.s of the Black and Caspian seas (St. Petersburg and Leipsic, 1849), and Petermann's Mittheilungen, iii., vii., 1869, contain valuable information on this sea.