1911 Encyclopædia Britannica/Bosporus

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BOSPORUS, or Bosphorus (Gr. Βόσπορος = ox-ford, traditionally connected with Io, daughter of Inachus, who, in the form of a heifer, crossed the Thracian Bosporus on her wanderings). By the ancients this name, signifying a strait, was especially applied to the Bosporus Cimmerius (see below), and the Bosporus Thracius; but when used without any adjective it now denotes the latter, which unites the Black Sea with the Sea of Marmora and forms part of the boundary between Europe and Asia. The channel is 18 m. long, and has a maximum breadth at the northern entrance of 23/4 m., a minimum breadth of about 800 yds., and a depth varying from 20 to 66 fathoms in mid-stream. In the centre there is a rapid current from the Black Sea to the Sea of Marmora, but a counter-current sets in the opposite direction below the surface and along the shores. The surface current varies in speed, but averages nearly 3 m. an hour; though at narrow places it may run at double this pace. The strait is very rarely frozen over, though history records a few instances; and the Golden Horn, the inlet on either side of which Constantinople lies, has been partially frozen over occasionally in modern times. The shores of the Bosporus are composed in the northern portion of different volcanic rocks, such as dolerite, granite and trachyte; but along the remaining course of the channel the prevailing formations are Devonian, consisting of sandstones, marls, quartzose conglomerates, and calcareous deposits of various kinds. The scenery on both sides is of the most varied and beautiful description, many villages lining each well-wooded shore, while on the European side are numerous fine residences of the wealthy class of Constantinople. The Bosporus is under Turkish dominion, and by treaty of 1841, confirmed by the treaty of Berlin in 1878 and at other times, no ship of war other than Turkish may pass through the strait (or through the Dardanelles) without the countenance of the Porte. (See also Constantinople.)