CLIMATE OF EGYPT. 881 transversely or obliquely to the norniul ranges. The bottom of the trough between two parallel ridges presents a tolerably good footing to the wayfarer ; but progress is extremely difficult on the slopes of the crumbling sandhills. No springs rise at the foot of the dunes ; no living thing dwells in this region of death, where travellers themselves plodding wearily and silently through the sands seem like phantoms to each other. Climate of Egypt. The climate of Egypt, although very different in the neighbourhood of the Meditorranoun and in the narrow valley of the Upper Nile skirted on both sides by the escarpments of the desert plateaux, is remarkable especially for the uniformity of its phenomena, the regular course of the atmospheric currents, and the dryness of its atmosphere. In its meteorological conditions, the valley of the Nile, that is to say, Egypt, resembles the Red Sea. As in all mountain gorges, the aerial currents which penetrate into this marine basin follow it regularly in the direction of its length. Here they become changed either into the shemal, or wind of the Gulf of Suez, or else into the mHiab, or wind of the Gulf of Aden. Thus the north-east monsoon, which in the Indian Ocean prevails from October to March, changes its direction on entering the Gulf of Aden, where it becomes a south-east wind. So also the khamsin, which comes from the Libyan desert — that is, from the west — on reaching the Red Sea is deflected northwards parallel with both coasts. In the same way the western, northern, and north-eastern currents from the Mediterranean, all alike take a direction contrary to that of the south- east monsoon. On the other hand, the land and sea breezes, which alternate with such remarkable regularity on most of the tropical coast lands, play a very feeble part along the shores of the Red Sea. Utilised to a limited extent by sailing vessels for a few hours of the day, they are borne now to the north, now to the south in the general current of the atmosphere. They acquire a little influence only at the change of seasons in spring and autumn. Under the action of the alternating northern and southern breezes, a correspond- ing movement takes place in the Suez Canal, where in summer the Mediterranean waters are driven towards the Red Sea, in winter, those of the Gulf of Suez towards the Bay of Pelusiura. About 14,000,000,000 cubic feet of water thus ebb and flow from season to season, at a velocity varying from 6 to 26 inches per second. In the Nile Valley, as in the long trough of the Red Sea, all the winds, whatever their original direction, change in the same way to currents setting north and south. In Lower Egypt alone, where no obstacle intervenes to obstruct their course, they blow from all quarters of the compass, according to their original direction and modifying local influences. The alternation of the aerial currents is regulated in the Nile Valley with less uniformity than in the Red Sea. In this longitudinal basin they succeed each other in almost rhythmical order. In winter the south-east monsoon, which rushes impetuously into the Strait of Bab-el- Mundeb, acquires the ascendancy, and makes itself felt at times as far as the neighbourhood of Suez. In summer, on the
