Page:The journal of the Royal Geographic Society of London. Volume 34, 1864. (IA s572id13663720).pdf/324

114 The reason of this is evident. Mountains are the reservoirs of a country, and the nearer that country is to the Equatorial line, the loftier should be its mountains in order to afford a perennial supply of water. But Arabia, with the single exception of ’Oman, presents no mountains of sufficient elevation to answer that purpose. The range of hills near the coast is generally far too low— it varies, in fact, from about 500 to 1000 feet in height, but seldom surpasses it; and the centre is a mere steppe or plateau, whose table-lands barely attain 3000 feet above the sea-level, though they are decorated by the inhabitants with the title of mountains, for want of better.

Hence, whatever rain falls on these steppes, and rain does fall even heavily at times, especially in the winter and early spring, is soon absorbed in the crevasses of the loose soil, or in the sandy intersecting valleys, and thus collects underground, instead of above it. Near the sea-coast only, where the rim of the plateau breaks off abruptly, or gradually dips down, occasional running sources burst out, whose origin is to be sought for in the underground waters of the central lands. But as the coast itself is in general girt by a narrow mountain-chain close on the sea-shore, such rivulets very seldom reach the sea, much less form rivers worthy of finding a place in a geographer’s map.

Of the abundance of subterranean water in central Arabia, and of the means of irrigation there employed, I shall say more in the progress of this narrative.

The same causes occasion a similar and an even greater dearth of above-ground water in the desert itself. Its regions are considerably elevated above the sea-coast, being as it were backed up on all sides by the surrounding range already mentioned; but they are again lower than the central steppes; their average alti¬ tude varies, as far as I could judge from rough and half guesswork mensuration, from 500 to 1000 feet above the sea,—perhaps a little more. Being thus neither high enough to attract the passing clouds, nor low enough to give outlet to the confined underground waters, and presenting a very chinky and fissured soil, they naturally remain drier than either the central plateau or the coasts themselves.

However, this desert or deserted land has its waters too, only they are in general to be sought for at a considerable distance underground: I have here seen wells of above a hundred feet in depth, though at times the water comes nearer the surface, especially, as we should naturally expect, in the lower grounds of such tracts. At times a long line of wells marks out the course of a subterraneous stream. Thus for the whole length of Wadi Sirhan, from the Hauran in Syria to the Djowf, water is everywhere to be got at by digging for 10 or 15 feet in depth, and occasionally