Arabia has well-defined boundaries everywhere except on the north. Eastward are the waters of the Persian Gulf, the Strait of Ormuz and the Gulf of Oman. The entire southern coast is washed by the Indian Ocean which reaches to Bab-el-Mandeb “The Gate-of-tears,” from which point the Red Sea and the Gulf of Akaba form the western boundary. The undefined northern desert, in some places a sea of sand, completes the isolation which has led the Arabs themselves to call the peninsula their “Island” (Jezirat-el-Arab). In fact the northern boundary will probably never be defined accurately. The so-called “Syrian desert,” reaching to about the thirty-fifth parallel might better be regarded as the Arabian desert, for in physical and ethnical features it bears much greater resemblance to the southern peninsula than to the surrounding regions of Syria and Mesopotamia. Bagdad is properly an Arabian city and to the Arabs of the north is as much a part of the peninsula as is Aden to those of the southwest. The true, though shifting, northern boundary of Arabia would be the limit of Nomad encampments, but for convenience and practical purposes a boundary line may be drawn from the Mediterranean along the thirty-third parallel to Busrah. Thus the shores of Arabia stretch from Suez to the Euphrates delta for a total length of nearly 4,000 miles. This coast-line has comparatively few islands or inlets, except in the Persian Gulf. The Red Sea coast is fringed by extensive coral reefs, dangerous to navigation, but from Aden to Muscat the coast is elevated and rocky, and contains several good harbors. Eastern Arabia has a low, flat coast-line made of coral-rock with here and there volcanic headlands. Farsan, off the Tehamah coast, famous as the centre for Arab slave-dhows; Perim, where English batteries command the gate of the Red Sea; the Kuria-Muria group in the Indian Ocean; and the Bahrein archipelago in the Persian Gulf, are the only important islands. Socotra, although occupied by an Arab population and historically Arabian, is by geographers generally attached to Africa. This island is however under the Indian government, and, once Christian, is now wholly Mohammedan. The greatest length of the peninsula is about 1,000 miles, its average breadth 600, and its area somewhat over 1,000,000 square miles. It is thus over four times the size of France or larger than the United States east of the Mississippi River.