Bosporus, or Bosphorus, a narrow strait about seventeen miles long, and from a third of a mile to two miles wide, connecting the Black Sea with the Sea of Marmora, and separating Europe from Asia. It is strongly defended by forts, and no ship of war belonging to any nation other than Turkey may pass through it without the permission of Turkey. On its W. side stands Constantinople on a gulf of the Bosporus called the Golden Horn. The banks of the channel present beautiful scenery, being lined with palaces, kiosks, villages, and beautiful residences, interspersed with magnificent, gardens. From the northeast there is a continual surface-current, with a reverse under-current, The channel is about 30 fathoms deep and the navigation safe.