The principal drainage-basins are shown on the small scale map on Plate II. The westward drainage ultimately reaches the Nile by the three main trunk wadis of Shait, Kharit, and Alaqi; Shait and Kharit enter the Nile Valley at Kom Ombo, while Alaqi debouches near Dakka. The eastward drainage is much more complex, the principal trunk wadis, such as Um Khariga, Gemal, Khoda, Rahaba, Hodein, Ibib, Di-ib, and Serimtai, being separated by very numerous minor wadis draining independently to the sea.[37] Nearly all the wadis contain vegetation in the form of trees and bushes, and plant life flourishes as a rule far more luxuriously in wadis draining seawards than in those leading to the Nile. Feqoh, Naam, and the lower reaches of Hodein are, however, exceptionally barren. Forming, as they do, the only possible roads, furnishing the entire supply of camel food, and containing most of the wells, the wadis are to the desert what the Nile is to Egypt proper. The intervening mountains are of no interest to the Arabs, except when they contain water-reservoirs. Hence the place-naming starts from the wadis, even the smallest of which have names unless they are barren. Mountains are generally named after the nearest wadi, and may thus have two names when situated between two wadis, the particular name used depending on which side the mountain is seen from. =Coast-line.= The coast-line of this part of Egypt is somewhat irregular, the peninsula of Ras Benas forming a prominent projection in latitude 24°. In the south part of the area the eastward extension of the country, culminating in Ras Hadarba (Cape Elba of existing maps), is very marked, extending nearly to 37° of east longitude. The coast is almost entirely fringed by coral reefs, passage through which is only possible at certain points, and then only with the utmost care in navigation.[38] Between the feet of the mountains and the sea there extends a gently sloping plain, varying in width from about eight to twenty-five kilometres, covered with sand, over which the drainage meanders in shallow courses, often only traceable by the vegetation which occurs along them. A rather surprising result brought out by the levelling observations is that the slope of the coast plain, even where it looks flattest and sandiest, is as steep as the floors of some of the wadis draining on to it, and several times more steep than the beds of the wadis which drain westwards to the Nile, its fall seawards averaging six metres per kilometre and reaching over ten metres per kilometre in some sections. =Climate.=