PERSIAN GULF, an arm of the Indian ocean which penetrates between Arabia and Persia to the extent of 050 English in. in a general north-westerly direction. Its breadth varies from 55 in. at the month to 250 tu., and the area is estimated at 117,300 sq.m., from which about 1930 sq.m. must be subtracted for the islands, which are scattered over the western half, or lie close inshore along the eastern side. The chief of these islands are Ormuz (q.v.), at the mouth; Kishm, 910 sq.m. in extent; and the Bahrein islands (q.v.), chief of which is Samak. The great pearl bank stretches along the west ern Side from Ras Hassan to nearly hnlf-way up the gulf. The coast is mostly formed of calcareous rocks. On the Arabian side it is low and sandy, occasionally broken by mountains and cliffs; while, on the Persian side, it is higher and abrupt, with deep water close inshore, owing to the mountain-ranges of Fars and Laristau running close to the water's edge. The islands are partly of limestone and partly of ironstone, and are generally destitute of springs, barren, desolate, and presenting numerous traces of vol canic eruptions. With the exception of the Shat-el-Arab (q.v.), the Persian gulf receives
only insignificant streams. Its eastern side presents abundance of good anchorage, either in the numerous bays or in the lee of islands. The greater portion of its shores now belongs to the imam!) of Muscat. The coasts of the golf have been explored by successive British expeditions, the last of which, in 1821-25, made it complete trigono metric survey of the Arabian shore, The older of the periodic currents in this gulf is precisely the reverse of that of the 'Zed sea (q.v.) currents, as they ascend from May to October, and descend from October to May.
Oriental geographers give to this gulf the name of the "Green sea," from a remark able strip of water, of a green color, which lies along the Arabian coast. It is strange that from the time of Nearchus, the admiral of Alexander the great, who was the first to make the Persian gulf known to Europeans, the Persians have never ruled supreme over its surface.