412 JOURNEY TO CENTRAL AFRICA.

were constantly forming and changing shape, and the sand vibrated along their edges or scudded in swift ripples over the plain, with that dry, sharp sound one hears in winter, when the " North-wind's masonry" is going on. The air was withering in its fierce heat and occasioned intense thirst, which, fortunately, we were able to relieve. The storm grew more violent and the burning labyrinths of sand more intricate, as we advanced. The path was hidden under drifts five or six feet in height, and the tall yellow walls were creeping every minute nearer, to cover it completely. The piles of stones, however, which the Arabs have made on the tops of the ridges and replace as often as they are thrown down, guided us, and after three hours and a half in a spot which might serve as the fourth circle of Dante's Hell, we emerged on the open plain and saw again the Mountain of Thirst, which had been hidden all this time. The camels, which were restless and uneasy in the sand, now walked more cheerily. The sun came out again, but the sky still retained its lurid purple hue. We all drank deeply of the brown leathery contents of our water-skins and pushed steadily onward till camping-time, at sunset. While the storm lasted, the Arabs crouched close under the flanks of the camels and sheltered themselves from the sand. Achmet and the Congolese merchant unrolled their turbans and muflled them around their faces, but on following their example I experienced such a stifling sensation of heat that I at once desisted, and rode with my head exposed as usual.

We halted in a meadow-like hollow, full of abundant grass, in which the weary camels made amends for their hardships.

The wind howled so fiercely around my tent that I went to sleep expecting to have it blown about my ears before morn-