or MEHUN, an island in the Strait of Bab-el-Mandeb, off the coast of Yemen in Arabia, and having its southern extremity in N. Lat. 12° 38', E. Long. 43° 23'. In form it is oval, 34 miles in length from W.N.W. to E.S.E., by 2½ in breadth; and it divides the entrance of the Red Sea into two channels, called the Great and Little Straits respectively; the former, between Perim and the African coast, being 13 miles broad, and the latter, formed by the island and Cape Bab-el-Mandeb, 1¾. The Little Strait is the one most frequently used by vessels entering the sea, as it is quite safe, though varying from 7 to 13 fathoms in depth, and as it affords good anchorage; whereas in the Great Strait, where the depth varies from 13 to 25 fathoms, there are only a few places where anchorage can be obtained; but during the night, with a favourable breeze, the wider passage is to be preferred. The island is a bare black rock, without water, and almost entirely destitute of vegetation; but it has on the S.W. side a magnificent harbour, more than 1½ mile in length, and from a half to three quarters of a mile in breadth, with a depth of 7 or 8 fathoms. It is capable of containing forty men-of-war; and the entrance is safe, being about half a mile wide, and 16 fathoms deep. The island of Perim commands the entrance of the Red Sea; and for this reason it has been twice occupied by the British in order to defend the approach to India. The first occasion on which it was occupied was in 1799, in order to guard against the designs of the French, who were then in possession of Egypt. The island was, however, abandoned in 1801, when that danger had passed away. In recent times, the project of the Suez Canal has given rise to similar apprehensions; and the island was a second time occupied, February 1, 1857, and formally taken possession of on the 14th of the same month. Since that period fortifications have been erected on the island, under the guns of which all vessels have to pass that sail through the straits.