Note 13 — LIST OF PLATES.

Oïridh, “devils”; Hindustani, latūr; Arabic, sheitan. These are in the desert what waterspouts are in the sea, and might be called sandspouts were not “spout” indescriptive of the appearance in either case.

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.