These Touareg camels are of the very best race. They can go from three to seven days without drinking, and for two without eating. Their speed surpasses that of the horse, and they obey with intelligence the voice of the _khabir_, or guide of the caravan. They are known in the country under the name of _mehari_. Such were the details given by the doctor while his companions continued to gaze upon that multitude of men, women, and children, advancing on foot and with difficulty over a waste of sand half in motion, and scarcely kept in its place by scanty nettles, withered grass, and stunted bushes that grew upon it. The wind obliterated the marks of their feet almost instantly. Joe inquired how the Arabs managed to guide themselves across the desert, and come to the few wells scattered far between throughout this vast solitude. “The Arabs,” replied Dr. Ferguson, “are endowed by nature with a wonderful instinct in finding their way. Where a European would be at a loss, they never hesitate for a moment. An insignificant fragment of rock, a pebble, a tuft of grass, a different shade of color in the sand, suffice to guide them with accuracy. During the night they go by the polar star. They never travel more than two miles per hour, and always rest during the noonday heat. You may judge from that how long it takes them to cross Sahara, a desert more than nine hundred miles in breadth.” But the _Victoria_ had already disappeared from the astonished gaze of the Arabs, who must have envied her rapidity. That evening she passed two degrees twenty minutes east longitude, and during the night left another degree behind her. On Monday the weather changed completely. Rain began to fall with extreme violence, and not only had the balloon to resist the power of this deluge, but also the increase of weight which it caused by wetting the whole machine, car and all. This continuous shower accounted for the swamps and marshes that formed the sole surface of the country. Vegetation reappeared, however, along with the mimosas, the baobabs, and the tamarind-trees. Such was the Sonray country, with its villages topped with roofs turned over like Armenian caps. There were few mountains, and only such hills as were enough to form the ravines and pools where the _pintadoes_ and snipes went sailing and diving through. Here and there, an impetuous torrent cut the roads, and had to be crossed by the natives on long vines stretched from tree to tree. The forests gave place to jungles, which alligators, hippopotami, and the rhinoceros, made their haunts. “It will not be long before we see the Niger,” said the doctor. “The face of the country always changes in the vicinity of large rivers. These moving highways, as they are sometimes correctly called, have first brought vegetation with them, as they will at last bring civilization. Thus, in its course of twenty-five hundred miles, the Niger has scattered along its banks the most important cities of Africa.”