Bos'phorus, or Bosporus (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. 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 Bosphorus, is Scutari. The length of the Bosphorus is about 17 miles, with a breadth of from little more than 1/3 mile to 2 miles, and its average depth is about 30 fathoms. None but Turkish war-ships may navigate it without consent of the Sublime Porte. See Black Sea and Kertch.