Franco-British Convention of Dec. 23 1920, affect it (see SYRIA). The limits of the various independent states of the peninsula, with the exception of the N. boundary of the Aden protectorate, all remain equally undefined. A natural frontier on the N. runs in an irregular curve from Akaba ('Aqaba) first N.E. and then S.E. to the Persian Gulf, following the fringe of cultivation, which fluctuates according as the nomadic or sedentary popula- tion is the stronger. This line excludes Kerak, but leaves the transition area of the Hamad or Syrian Desert within Arabia, to which, both physically and ethnographically, it seems to belong.
Topography. Up to 1914, even the best knowledge of Arabia was sketchy, but considerable advance has since been made by the discoveries of recent travellers and as a result, direct or indirect, of war operations. The progress to be noted falls under three main heads: new light has been thrown on the drainage of the peninsula; the positions of a number of places, previously very imperfectly known or only guessed at, have been accurately fixed; and a vast amount of topographic and ethnographic detail has been accumulated.
The compilation of the map of Arabia on the million scale has kept pace with discovery. For this purpose, the route traverse in northern and central Arabia from Huber's Journal, extending over 3,000 m., was replotted on a large scale and formed a groundwork on which to place the more hurried surveys of Wallin, Palgrave, Doughty, etc. All the labours of recent travellers, starting with Leachman (1910), and ending with Bell (1914), were reconsidered from the originals and adjusted with due regard to the proportionate value of each, while the in- formation collected by Col. Lawrence during the World War and the surveys of Philby were incorporated. The work of compilation was undertaken by D. Carruthers in 1914 and in 1921 was still in progress. Provisional sheets covering the northern half of the country had already been issued.
The course of the main watershed of Arabia can now be traced with general accuracy. Prolonged northward from the highlands of Yemen and Asir, it passes inland between Taif and Wadi Turaba and runs E. not W. as was previously supposed of the Hejaz railway through the Kheibar harm, or. lava outcrop. Perhaps some of the higher peaks of the 'Aweiridh ridge overtop it.
Wadi Hamdh, the main drainage basin of the short western slope of Arabia, previously thought to have its head-waters in the vicinity of Medina, at about lat. 24 N., in all probability has its source in W. 'Aqiq, at least 3 farther S., thus giving it a total length of 700 to 800 m. including windings. The 'Aqiq, rising S.W. of Taif, passes well to the E. of Mecca and W. of Medina and is said to take the name W. Shaiba between these two towns. Some doubt remains whether the Shaiba discharges wholly into the Hamdh just N. of Medina, or whether it also forms a tributary eastward in W. Rumma (Rima). Wadi 'Ais, coming from the N., and W. Jizil from the S., and joining W. Hamdh in the plain of Jurf are its two main afflu- ents, and their courses, together with the middle reaches of the Hamdh, have been explored in great part and mapped.
Much new information has been obtained as to the drainage of the long eastward slope effected mainly by the great wadi sys- tems of the Dawasir, Sahaba and Rumma (naming from S. to N.). The town of Dam, in W. Dawasir, central Arabia, previously mapped near lat. 23 N., has had its position definitely fixed in lat. 20 27' N. and long. 44 40' E. The direction of the course of W. Dawasir, a matter long in dispute, proves to be S.E. towards the Ruba'el Khali, or Great Southern Desert, and not N.E. as the old maps show. The point of junction of the important Asir wadis - Ranya, Bisha and Tathlith is in all probability in the plain of Hajla about 50 m. N.W. of Dam. As to W. Sahaba, which has a practical monopoly of the surface-waters of the central mass of Arabia and the drainage of which trends to the sea at the southern end of El Qatar, it was found to have its remotest head-waters in W. Sirra in the very heart of the peninsula. Under the name of W. Birk, the Sirra breaks through the Tuwaiq plateau and, turning northward as W. 'Ajaimi, joins W. Hanifa some 60 m. S.E. of Riyadh (lat. 24 37' N,, long. 46 41' E.). W. Hanifa ultimately falls into the Sahaba, but the latter probably carries no surface-water, at any time, farther than the western fringe of the Dahana, about long. 48 E. Wadi Subai, rising somewhere in lat. 22 N., is prob- ably the most southern tributary of W. Rumma.
ARABIA
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