and sky seemed to mingle in a chaos of confusion, a pandemonium of sound. Then the wind subsided as abruptly as it had arisen, leaving a thick veneer of red-brown dust on everything. The air became fresh and clear again. The palm-fronds stirred ever so slightly in the gentle night breeze. One by one the stars came out, as at nightfall the lights are turned on in a great city. Peace and utter silence descended on the desert. The Sahara slept once more. [Illustration: A LANDMARK FOR THOSE WHO NAVIGATE THE SEA OF SAND In order to prevent caravans from losing their way in the sandy waste, the French have marked the great trade-routes across the Sahara at ten-kilometer intervals with lofty towers of stone; the curious superstructure atop the _bassourab_, or camel-tent in which the women travel, enables the tribe or caravan to be identified from afar] But the morning light revealed an astounding transformation. The whole landscape had been remade. Nothing was the same. Hills stood where hollows had been before, and ridges had been replaced by rifts. Even our Arab guide, who knew the desert as a housewife knows her kitchen, seemed to have difficulty in orienting himself and stood for some minutes alternately glancing at the sun and studying the transformed terrain. For the first time I understood how it was possible for caravans to lose their way when overwhelmed by a sand-storm and to perish in this dreadful land from thirst and exhaustion. In order to lessen the chance of such disasters, however, the French government has undertaken the task of marking the main trade-routes across the desert with lofty signal-towers of stone, some of them fifty feet in height. Set on the highest eminences, about ten kilometers apart, they rear themselves above the sandy sea like lighthouses along a perilous coast. In places we could see them, through the glasses, rising at intervals across the desert, marking the courses of the great trade-tracks which run down to Tchad, to Zinder, and to Timbuktu. * * * * *