Mysteries of the Libyan Desert

by W. J. Harding King

A very similar state of things occurs in the Atlantic and Pacific oceans, where the cold air rushes in towards the equator from both north and south to form the trade winds. These winds, however, do not blow at right angles to the equator, for the earth in its rotation slips away, as it were, from under the surrounding atmosphere, with the result that the trade winds blow from the north-east and south-east, in the northern and southern hemispheres respectively.

But instead of blowing from the north-east, as would be expected from the character of the trade winds, the wind in the Libyan Desert comes from slightly to the west of north, which at first sight appears rather puzzling.

The explanation of this peculiarity lies, I believe, in the fact that to the east of Egypt—across the Red Sea—lies a like track of country to the Libyan Desert in the shape of the Arabian Desert, where very similar conditions prevail. The Red Sea, which separates the two, being too narrow to greatly affect the situation, the air overhanging the eastern part of the Mediterranean has also to take the place of the heated atmosphere rising from Palestine and a considerable part of Arabia, and consequently tends to draw in that direction.

Various phenomena of light and electricity, seldom or never seen in other climates, are to be found in the desert. I several times saw what appeared to be a large star suddenly flash up and disappear immediately. This I believe to have been not a meteor, but some form of electrical phenomenon, as I usually saw it after a sandstorm, when the air was full of fine electrified sand.

Solar phenomena are sometimes very conspicuous in the desert, the zodiacal light that follows the sunset being often very clearly seen, in the form of a semi-elliptical portion of the sky showing brightly above the horizon, after the sun had disappeared, and shining with sufficient strength to give quite an appreciable light.

There was another phenomenon that I saw in this desert that I have never seen alluded to by other travellers. Sometimes at sunset luminous lines would appear in the eastern sky radiating from a point opposite to the setting sun. These lines were never very pronounced, but at the same time were quite clearly visible. On one occasion, instead of luminous lines, dark ones appeared instead.

Another peculiarity of this part of the desert was the way in which a sandstorm would sometimes spring up without any appreciable change in the strength or direction of the wind. I concluded this to be due to a change in the electrical condition of the atmosphere.

The connection between the winds of this desert and its geography is so close that I have included them both in this section. The chief effect of the wind on the desert sands is, of course, to be seen in the dunes. In addition to those mentioned when dealing with the native information I collected, there is a large area in the Farafra depression covered with sand hills and those in the neighbourhood of Bu Mungar which have been previously mentioned.

Several narrow belts of dunes are also to be found starting in the great depression between Siwa and Cairo. These belts, too, run roughly from north to south; but with one exception they all die out before reaching the latitude of Farafra Oasis.

The effects of the violent desert gales was everywhere to be seen. On the limestone plateau, on the way to Kharga Oasis, and on the Derb el Tawil very fine examples of sand erosion are visible.