a wind which moves in a spiral direction, as well as horizontally, which is exceedingly rapid and impetuous, but only of short duration.

Dr Franklin's opinion of the origin of whirlwinds has been already given in the article WATER-SPOUT. If his theory be true, it will follow, that no hurricane ever can be so violent as to remove an obstacle of the size of only one cubic inch, provided that was supported by a power equivalent to 15 pounds; for this is the utmost force of the atmosphere when rushing into a perfect vacuum, which never could take place in the centre of a whirlwind or water-spout. Indeed, notwithstanding the dreadful effects sometimes observed from hurricanes and whirlwinds, we shall easily perceive, that the utmost of their power always falls very far short of this. The diminution of the specific gravity of the air by only one-fourth in the middle of the column, would produce such an influx of air from all quarters, that an obstacle presenting a surface of one foot square, would require a force of 504 pounds to prevent it from being carried away; which the strongest walls that can be built by human art could scarce resist. Now, even the tenth part of this, or the diminution of the gravity of the atmosphere by one-fortieth part, would produce a pressure of upwards of 50 pounds on every square foot of surface, which, it is to be doubted, whether any of our common houses could resist.

Some philosophers ascribe the vacuum in the atmosphere, to which, according to Dr Franklin's theory, whirlwinds are owing, to a stream of electric matter rushing with violence into the atmosphere out of the earth. But they do not inform us how this matter comes to be accumulated in that part of the earth; what induces it to pass out of the earth; how it passes invisibly through pure air; or what serves it for a conductor. It seems to be the fashion among certain philosophers to ascribe every phenomenon, with the cause of which we are unacquainted, to electricity. But this is merely substituting a new name, and serves rather to retard than advance our knowledge of nature.

Some kinds of whirlwinds move with a flow motion, and are injurious only by their vortex; while others seem to do mischief as well by their progressive as their whirling motion. Of this kind are those called typhoons; which, by their frequently following the course of rivers, seem thus also to discover their electrical origin. Of the destructive effects of these, we have an instance in what happened in Charlestown in South Carolina, on the 1st of June 1761. It was first observed about noon, on land, upwards of 50 miles west by south of Charlestown, and destroyed several houses, &c. as it passed along, in many places making wide avenues through the woods; from whence every tree and shrub was torn up, and great branches of trees were driven about in the column as it passed along. It directed its course to Ashley river, down which it came with surprising velocity; in its appearance resembling a column of smoke or vapour, whose motion was very irregular and tumultuous. Its momentum was so great, that Ashley river was ploughed to the bottom, and the channel laid bare. As it came down this river, it made a constant noise like thunder; its diameter being computed about 300 fathoms. It was met at White Point by another of the same kind which came down Cooper's river, but with inferior strength; however, on their meeting together, the agitation of the air was much greater, while the clouds, which were driving in all directions to the place, seemed to be precipitated, and whirled round with incredible velocity. It then fell upon the shipping in the road; entirely destroying some, and damaging others; being scarce three minutes in its passage, though the distance was near two leagues. In that short time it did damage to the amount of 20,000l.; and had not its direction been altered by that gust which came down Cooper's river, it must have totally destroyed Charlestown, as no obstacle whatever seemed capable of resisting its fury.