_Winds and Rain._—In the heart of the Sahara, where rain is so rare a meteorological phenomenon, the wind is the high arbiter of each day’s weather. The weather is fine when the wind is light, and bad when it is strong; in the latter case nothing is to be seen but whirling columns of sand, raised by the north-east wind, blowing in stormy gusts and covering the whole landscape with a thick dry mist of brownish dust that penetrates everywhere and is very painful to the eyes, so that one does well on such occasions to wear motor-goggles to avoid ophthalmia. These north-east winds blow more or less violently for a great part of the year, sometimes for a few hours only each morning, sometimes for whole days and nights. I may say that we were able to note a fair correlation between the oscillations of the curves of the registering barometer and thermometer and the force and duration of these winds; they usually coincide with low temperatures and high atmospheric pressure, while the light winds or the dead calm accompany low pressure and high temperatures. Taking as a basis the information furnished by the natives, borne out by our four years of regular observations, it may be said that, as a general rule, the north-east wind reigns supreme over Borkou and the neighbouring districts from October to May or June (that is to say, from about the autumnal equinox to the summer solstice); whereas in July, August, and September still weather prevails, alternating with gentle west-south-westerly winds. It is these latter winds that bring with them from the Atlantic what little moisture nature measures out each year so parsimoniously to these dried-up lands. Then the sky clouds over almost every afternoon, but one’s hope of refreshing showers is vain; the heat thrown up from the scorched ground, and the rapidly rising temperature through which the raindrops fall towards the earth (a rise of about 3° Fahr. per 1000 feet), are enough to bring about their more or less complete evaporation before they reach the ground, and one sees long frayed streaks of grey cloud trailing almost along the ground, like unravelled skeins of wool, from which a few rare drops fall on the thirsty earth. When we took possession of Borkou the inhabitants assured us with one voice that it had not rained in their country for eleven years, thus putting back the date of the last rain to the year 1902; by a curious chance our entry into Faya (on 1 December 1913) was greeted by a little shower of utterly unlooked-for rain. The inhabitants saw in this downfall (unusual not only for that region, but for that season of the year) a happy omen for the rainy season of 1914, an omen which was realized, for in the month of August 1914 we had the satisfaction of registering about 90 mm. of rain at Faya. In 1915 the rainfall was hardly worth mentioning, and in 1916 about 35 mm.