The phenomenon is produced as follows:—A whirlwind arises at perhaps a height of five hundred feet. Its vortex decreases in diameter downwards until, on the desert surface, it is perhaps two or three feet in diameter, whirling round with great velocity, and with an upward spiral. When it passes over loose sand it carries with it all movable particles. The whole thing, like a whipping top in form, rises and falls and moves about. When it rises, and only the point of the whipping top rests on the surface, the circular motion is harmless. It sometimes goes up into the air and, when the circular motion is interrupted, drops sand and small bushes over a large area. When depressed, and when the diameter of the whirlwind reaches twenty or thirty feet, it has great force, and a camel will lie down, blinded, and fearing to be blown over. These “devils” march or dance about the desert in parties often of ten or twelve, and look like weird giants on a sultry gloomy evening. The effect is heightened by the dead stillness outside the radius of gyration. They have been the subject of highly-coloured description by travellers, and the statement in the text is characteristically simple.
[14]There are three kinds of partridge in this desert. The most interesting, hitherto shot near Assuan only by Colonel Harkness, is the Amnoperdrix Heysii, a richly coloured bird with a tuft or pencil of white feathers behind each ear.
[15]The Imperial porphyry, the Rosso Antico, is quarried here. It was said of the legitimate descendants of the Roman emperors that they were “porphyrogeniti,” or born in the purple, meaning that they were born in a chamber lined with this stone, to which chamber access was permitted only to the Emperor’s rightful wife. The quarries, after lying idle for 1700 years, are now worked by Mr. Brindley of London.
[16]Lycium, sp.?
[17]The seeds were raised at Great Carlton, and some of the young plants transferred to the Royal Gardens, Kew. Among them—Moringa aptera, Cassia obovata (the senna of commerce), Capparis spinosa, Zygophyllum album. Before mineral oils were introduced the oil of Ben, produced from the moringa aptera, was used by watchmakers.
[18]The inscription has not been seen since Sir Gardner Wilkinson’s visit. The text is given, in translation, in a paper on the Eastern Desert Proc. R. G. S., November, 1887. The original Greek is in Proc. R. G. S.
[19]These mountains support several hundred sheep and many half-wild donkeys. The wild ass is still found to the south. The sheep feed on the leaves of the acacias, which are shaken down for them by the shepherds, who use long hooks to shake the branches. The sheep are thus entirely dependent on the shepherd for food, and follow him eagerly the moment they see him take up his hook.
[20]The kurbatch is a long tapering strip cut from the hide of a hippopotamus. It is hard, but flexible, like stiff indiarubber.