He instinctively noted these signs; and on board ship would have heeded them,--so far as to have alarmed the sleeping watch, and counselled precaution. But stretched upon terra firma--not so very firm had he but known it--between two huge hills, where he and his companions were tolerably well sheltered from the wind, it never occurred to the old salt, that they could be in any danger; and simply muttering to himself, "the storm be blowed!" he laid his weather-beaten face upon the pillow of soft sand, and delivered himself up to deep slumber. The silent prediction of the sailor turned out a true forecast. Sure enough there came a storm; which, before the castaways had been half an hour asleep, increased to a tempest. It was one of those sudden uprisings of the elements common in all tropical countries, but especially so in the desert tracts of Arabia and Africa,--where the atmosphere, rarefied by heat, and becoming highly volatile, suddenly loses its equilibrium, and rushes like a destroying angel over the surface of the earth. The phenomenon that had broken over the arenaceous couch,--upon which slept the four castaways,--was neither more nor less than a "sand-storm;" or, to give it its Arab title, a _simoom_. The misty vapor that late hung suspended in the atmosphere had been swept away by the first puff of the wind; and its place was now occupied by a cloud equally dense, though perhaps not so constant,--a cloud of white sand lifted from the surface of the earth, and whirled high up towards heaven,--even far out over the waters of the ocean. Had it been daylight, huge volumes, of what might have appeared dust, might have been seen rolling over the ridges of sand,--here swirling into rounded pillar-like shapes, that could easily have been mistaken for solid columns, standing for a time in one place, then stalking over the summits of the hills, or suddenly breaking into confused and cumbering masses; while the heavier particles, no longer kept in suspension by the rotatory whirl, might be seen spilling back towards the earth, like a sand-shower projected downward through some gigantic "screen." In the midst of this turbulent tempest of wind and sand--with not a single drop of rain,--the castaways continued to sleep. One might suppose--as did the old man-o'-war's-man before going to sleep--that they were not in any danger; not even as much as if their couch had been under the roof of a house, or strewn amid the leaves of the forest. There were no trees to be blown down upon them, no bricks nor large chimney-pots to come crashing through the ceiling, and crush them as they lay upon their beds. What danger could there be among the "dunes?" Not much to a man awake, and with open eyes. In such a situation, there might be discomfort, but no danger.