GIBRALTAR, Straits of, the narrow channel which separates the south of Spain from the north of Africa. The width at the narrowest part, between Cabrera Point and the opposite shore, is thirteen miles. We have an excellent chart of the straits by Don Vincente Tefino de San Miguel, with the additional observations of Captain H. W. Smyth, R.N., from which it appears that there is a continual current flowing from the ocean in the middle of the straits, which has a velocity varying from three to six miles per hour, and is three and a half miles in breadth. There are
two lateral currents, which have a mean breadth each of two and a half miles; but they change their direction with the changes of the tide. At the time of ebb these lateral currents have a velocity equal to that of the central one. The depth of the strait in the meridian of Cape St Vincent is 100 fathoms; but in passing upwards the channel regularly and rapidly deepens, until, opposite to Europa Point at Gibraltar, the depth of water is 1000 fathoms. It is remarkable, that though the oceanic current at the straits, and that of the Bosphorus at the Dardanelles, continually pour their waters into the Mediterranean, its level is not raised. But Dr Halley long ago showed the evaporation from its surface was fully equal to maintain it at the same level, notwithstanding those additions, and that of the rivers it received. The current is sufficiently strong to be dangerous to vessels sailing into the Atlantic, and can only be overcome by a brisk wind from the Levant.