These outbursts are preceded by great sultriness, the whole ground is hot, everything is burning, even in the shade one dare not touch metal; then in the east a cloud of dust arises, which indicates the coming storm; the clouds bank up with astonishing rapidity, and now it is time for people to make the best of their way home as quickly as they can. The dust-clouds, lighted up by the evening sun, show the exact direction of the storm; some are of an inky black, others gray, and in the distance they can be seen dashing up against one another, and forming, as it were, a series of hills and valleys; yet there is scarcely a leaf moving, and all nature seems hushed. Then the storm-clouds seem to touch the earth, there is a sudden rustling of the leaves; the distant houses are lost in obscurity, and now it is time to shut oneself up in one's house. In a few minutes day has been turned into night, the wind howls round the house, windows and doors creak and rattle, till one begins to think in another moment the house will fall about one's ears. Lights are used, for now it is blacker than the darkest night; the fine dust penetrates everywhere and covers everything; the heat is overpowering, one perspires at every pore, and the dust cakes on one's face and hands, giving one the feeling of being intensely begrimed and dirty; but there is nothing for it but to wait patiently for the return of daylight, when one rises with one's eyes and mouth full of dust, and nothing but a complete bath makes one feel in any degree clean again. These sand-storms are generally followed by heavy showers, which completely lay the dust. A tropical thunderstorm is also full of solemn grandeur--deafening peals of thunder and howling wind, followed by a veritable deluge, which seems to transform the country into a lake in a few minutes. These sudden storms are a source of no small danger to Omdurman, especially in the quarter where the mosque and market are situated. Here there is no outlet for the water, which overflows into the yards and houses, and melts the mud-built walls like sugar. During the first year or two of Omdurman's existence, and before the people had much experience, several of the huts collapsed during a storm, burying the inhabitants in their ruins. The intense obscurity which always accompanies these deluges adds still more to the general alarm. However, after about two days the whole town becomes dry again; the hot sun and thirsty earth soon absorb all the moisture, and one would scarcely know that rain had fallen.