[70] “The most decisive circumstance tending to show the great velocity of brisk winds,” says Dr. O. Gregory, “is that of the rapid passage of the celebrated aëronaut M. Garnerin, from London to Colchester. On the 30th of June, 1802, the wind being strong, though not impetuous, M. Garnerin and another gentleman ascended with an inflammable air-balloon from Ranelagh Gardens, on the south-west of London, between four and five o’clock in the afternoon; and in exactly three-quarters of an hour they descended near the sea, at the distance of four miles from Colchester. The distance of the places of ascent and descent is at least 60 miles; so that, allowing no time for the elevation and depression of the balloon, but, supposing the whole period occupied in transferring it in a path nearly parallel to the earth’s surface, its velocity must have been at the rate of 80 miles per hour. If, therefore, the wind moved no faster than the balloon, its velocity was then 80 miles per hour, or 117½ feet per second; a celerity but little less than the greatest assigned by Kraaft: and hence it is probable, that the velocity of very impetuous winds is not less than 130 or 140 feet per second.” Haüy’s Nat. Phil. vol. i, p. 282. [71] Mr. Bruce, who, in his journey through the desert, suffered from the simoon, gives of it the following graphical description. “At eleven o’clock, while we contemplated with great pleasure the rugged top of Chiggre, to which we were fast approaching, and where we were to solace ourselves with plenty of good water, Idris, our guide, cried out, with a loud voice, ‘Fall on your faces, for here is the simoon.’ I saw from the south-east a haze come, in color like the purple part of the rainbow, but not so compressed or thick. It did not occupy twenty yards in breadth, and was about twelve feet high from the ground. It was a kind of blush on the air, and it moved very rapidly: for I scarce could turn to fall on the ground with my head to the northward, when I felt the heat of its current on my face. We all lay flat on the ground as if dead, till Idris told us it was blown over. The meteor or purple-haze which I saw, was indeed passed, but the light air that still blew was of heat sufficient to threaten suffocation. For my part, I found distinctly in my breast that I had imbibed a part of it, nor was I free of an asthmatic sensation, till I had been some months in Italy, at the baths of Poretta, near two years afterwards.” Though the severity of this blast seems to have passed over them almost instantaneously, it continued to blow so as to exhaust them till twenty minutes before five in the afternoon, lasting through all its stages very near six hours, and leaving them in a state of the utmost despondency.