Bosporus (also BOSPHORUS, Latinised forms of a Greek word meaning 'ox-ford'), the ancient name of the channel which separates Europe from Asia, and connects the Black Sea (Euxine) with the Sea of Marmora (Propontis). It was so called, according to the legend, from Io, who swam across in the form of a cow. Afterwards, as the same name was bestowed upon other straits, this was designated the Thracian Bosporus. Both its south and north entrances have light-houses on either side. Its shores are elevated, and throughout its length the strait has on either side seven bays or gulfs, with corresponding promontories on the opposite side. One of these gulfs forms the harbour of Constantinople, or, as it is often called, the Golden Horn. Across the Golden Horn is Pera, and opposite the imperial city, on the other side of the Bosporus, is Scutari. The length of the Bosporus is about 17 miles, with a breadth of from little more than a third of a mile to two miles, and its average depth is about 30 fathoms. Both sides look highly picturesque from the deck of the steamers plying up and down the straits, being richly dotted with cypresses, laurels, and ancient plane-trees, and covered with palaces, kiosks, villages, villas, and gardens. At the middle of this strait, where it is about 2800 feet in breadth, Darius made his bridge of boats when he marched against the Scythians. The Bosporus has long been under Turkish control, and repeated European conferences, including that of Berlin in 1878, have confirmed the stipulation of the treaty made in 1841, that no ship of war belonging to any nation but Turkey shall pass through it without the consent of the Ottoman authorities. For map, see CONSTANTINOPLE.
The name of CIMMERIAN BOSPORUS was given by the ancients to the Strait of Kaffa (q.v.), also called the Strait of Yenikalé or of Theodosia. The country on both sides of the Cimmerian Bosporus formed, about 500 B.C., a kingdom which grew till it embraced the whole Crimea, and of which the capital was Panticapæum. Many of its kings were in close alliance with the Athenians, but it at length became tributary to the Scythians.