WHIRLWIND

, a wind that rises suddenly, is exceedingly rapid and impetuous, in a Whirling direction, and often progressively also; but it is commonly soon spent.

Dr. Franklin, in his Physical and Meteorological Observations, read to the Royal Society in 1756, supposes a Whirlwind and a waterspout to proceed from the same cause: their only difference being, that the latter passes over the water, and the former over the land. This opinion is corroborated by the observations of M. de la Pryme, and many others, who have remarked the appearances and effects of both to be the same. They have both a progressive as well as a circular motion; they usually rise after calms and great heats, and mostly happen in the warmer latitudes: the wind blows every way from a large surrounding space, both to the waterspout and whirlwind; and a waterspout has, by its progressive motion, passed from the sea to the land, and produced all the phenomena and effects of a Whirlwind: so that there is no reason to doubt that they are meteors arising from the same general cause, and explicable upon the same principles, furnished by electrical experiments and discoveries. See Hurricane, and Waterspout. For Dr. Franklin's ingenious method of accounting for both these phenomena, see his Letters and Papers, &c, vol. 1, p. 191, 216, &c.

WHISPERING-Places, are places where a Whisper, or other small noise, may be heard from one part to another, to a great distance. They depend on a principle, that the voice, &c, being applied to one end of an arch, easily passes by repeated reflections to the other. Thus, let ABC represent the segment of a sphere; and suppose a low voice uttered at A, the vibrations extending themselves every way, some of them will impinge upon the points E, E, &c; and thence be reflected to the points F, F, &c; thence to G, G, &c; till at last they meet in C; where by their union they cause a much stronger sound than in any part of the segment | whatever, even louder than at the point from whence they set out. Accordingly, all the contrivance in a Whispering-place is, that near the person who Whispers, there be a smooth wall, arched either cylindrically, or elliptically, &c. A circular arch will do, but not so well.

Some of the most remarkable places for Whispering, are the following: viz, The prison of Dionysius at Syracuse, which increased a soft Whisper to a loud noise; or a clap of the hand to the report of a cannon, &c. The aqueducts of Claudius, which carried a voice 16 miles: beside divers others mentioned by Kircher in his Phonurgia. In England, the most considerable Whispering places are, the dome of St. Paul's church, London, where the ticking of a watch may be heard from side to side, and a very soft Whisper may be sent all round the dome: this Dr. Derham found to hold not only in the gallery below, but above upon the scaffold, where a Whisper would be carried over a person's head round the top of the arch, though there be a large opening in the middle of it into the upper part of the dome. And the celebrated Whispering-place in Gloucester cathedral, which is only a gallery above the east end of the choir, leading from one side of it to the other. See Birch's Hist. of the Royal Soc. vol. 1, pa. 120.