The simoom is also an institution of the desert. The simoom is unmistakably a wind, and surely no one who has not had the experience can appreciate it. Even the West India hurricanes or the typhoons of the China Sea are more kindly. They have plenty of destructive energy, it is true, but the simoom has all this and much else besides. It comes not without warning, but the warning and the wind are not far apart. The approach of the simoom is a dense black cloud of whirling and seething fine dust. As it strikes one, the choking, suffocating blast of hot air and dust overcomes everything that has life. The caravan men and the animals as well turn their backs to the wind and lie down with faces close to the ground. In a minute or two the full strength of the blast is on and the simoom is picking up not only the fine rock waste, but the coarser fragments as well, and is hurling them along at Empire State Express velocity. One might as well try to face a hail of leaden bullets. It is a cruel blast that neither animal nor human being can withstand. The camels crouch with their heads pointing away from the wind and nostrils close to the ground; their drivers lie prone with faces in little hollows scooped in the sand. Perhaps the full blast of the simoom may last an hour--perhaps two or even three hours. In lighter strain it may continue a whole day. When, finally, it ceases the air is thick with fine dust; one can see scarcely a rod away. Sun and sky are hidden, and the blackness of a tornado or of a London fog prevails. The fine dust floating in the air may not settle for several days. Perhaps a week afterward there may be a haze that partly obscures the sun. The dust, finer than the finest flour, pervades everything in the desert. One's clothing is full of it; one's hair becomes harsh and matted; the skin becomes rough, cracks and peels; the eyes are inflamed; mouth, lips, and nostrils are swollen. But the great bodily discomfort resulting from the simoom does not last forever; it gives place to bodily irritation of some other sort, which is indeed a grateful change merely because it is a change. The sand dunes of the Sahara are interesting to those who are not compelled to travel among them, but to the unfortunates who traverse them they are almost heart-breaking. Imagine oneself standing on an elevation a few hundred feet higher than the surrounding country. There is but one landscape--waves upon waves of the loose rock waste, for convenience called sand, as far as the eye can reach. Sometimes the waves are in long windrows, but oftener they are short and choppy like the surface waves of midocean.