Towards noon we approached a less level region, where the ground was raised into slightly elevated mounds, all inclining in the direction from east to west. The heat was suffocating, on account of the east wind, which raised great clouds of sand: our lips were covered with it; our thirst became insupportable; and our sufferings increased in proportion as we advanced further in the desert. We fell in with two Tooariks, who were going to el-Arawan, and whom we took to be the scouts of a troop of these marauders. Fortunately they were alone. They were both mounted on one camel. On the left arm they had a leather buckler; by the side, a poniard; and in the right hand, a pike. Knowing that they should meet us in their route, they had brought no provisions with them, and trusted to the caravan for a supply. These robbers, who would have trembled at the slightest menace, if seriously made, took advantage of the terror which their name and the crimes of their tribe every where spread, and obtained whatever they demanded: in a word, the best of every thing was presented to them. On the one hand, there was a sort of rivalship in offering them whatever they chose to eat; on the other, to give them water, though it would be six days before we should come to any. At last, after they had staid with us three days, we had the satisfaction to see them depart, and to be delivered from their troublesome company. At four in the evening we encamped to pass the night, during which we were oppressed by excessive heat, caused by a dead calm. The sky was heavy and covered with clouds which seemed immoveable in the immensity of space. Still the heat continued intense. Before proceeding farther, I ought to inform the reader how I continued to make an estimate of the route. We travelled, at an average, about two miles an hour. At night we proceeded almost constantly in a northerly direction. Being afraid that my pocket compass would be noticed if I took it out to consult it, I judged of our course during the day by the sun; in the night, by the pole-star. It is by this star that the Arabs are guided in all their excursions through the desert. The oldest caravan conductors go first, to lead the way. A sand-hill, a rock, a difference of colour in the sand, a few tufts of herbage, are infallible marks, which enable them to recognize their situation. Though without a compass, or any instrument for observation, they possess so completely the habit of noticing the most minute things, that they never go astray, though they have no path traced out for them, and though the wind in an instant completely covers with sand and obliterates the track of the camels.