I shall here make some observations on the climate of Wadaï. Wind, storms, thunder, and lightning, are very frequent there at the time of the Roushach. Their violence is such, especially during the first days of autumn, that it is almost impossible to describe their effects. During the whole time that I remained in the country I scarcely ever saw rain that was not preceded by a great wind that darkened the atmosphere. These storms generally advance from the east, and, passing over Gauz, or sandy plains, raise immense whirlwinds of dust, and carry them to a great distance. At the commencement of the storm the horizon is wrapped in clouds, either black or dun red. Presently the thunder bursts forth with terrific rolls. The people, stricken with fear, run to hide themselves. The shepherds hastily gather together their flocks and urge them towards the villages. Those who are working in the fields hasten to the nearest shelter, or run wildly towards the villages. The traveller seeks the first refuge he can find, for, if he is found abroad, there is peril. The storm, like a haughty and terrible conqueror at the head of his black warriors, strikes and shatters whatever it meets with. Isolated trees are often torn up by the roots, crazy huts are borne away, and old enclosures beaten to the ground. Even the beasts instinctively take to flight. The whirlwinds come laden with sand and gravel, that strike people down as if hurled from a sling. When I first went to Darfur, on perceiving afar off these immense whirlwinds, I expected great clouds and showers to follow, but I was soon undeceived. These dusty masses are seldom brought by south or west winds. They are often the effects of violent gusts, without rain or thunder, and for this reason are the more dangerous, for the rain soon beats down the dust and sand, and restores tranquillity to the air. Sometimes, during a whole month, these violent burrascos blow every day, beginning in the afternoon. Generally, in the last days of autumn, they are entirely without rain. When they happen at night, they are commonly accompanied by frightful showers and thunder-claps. The lightning falls, setting fire to villages, and dashing trees to pieces. Mischief is announced by terrible detonations, accompanied by long trains of fire descending from the clouds. Many Wadaïans and Forians have assured me that they have dug pits in the earth, at the place where the thunder has fallen, and have found substances resembling ferruginous scoriæ. In the countries of Soudan where I have travelled the thunder is much louder and more terrible than in Egypt. I do not know what is the physical reason of this difference.