. Edinburgh New Philosophical Journal. . 66' Professor CErsted on Water-Spouts. water round the base of the water-spout forms a great wreath of elevated water, with a bubbling and foaming surface. The particles carried up in the water-spout at the same time acquire a spiral motion, owing to the whh-ling which is combined with it. The falling particles, as, for example, drops or minute solid substances, which, ere the water-spout reach- ed the earth, had been driven upwards, or descending rain-drops and hailstones, must also enter windings, which, however, cross the windings already mentioned ;
. Edinburgh New Philosophical Journal. . 66' Professor CErsted on Water-Spouts. water round the base of the water-spout forms a great wreath of elevated water, with a bubbling and foaming surface. The particles carried up in the water-spout at the same time acquire a spiral motion, owing to the whh-ling which is combined with it. The falling particles, as, for example, drops or minute solid substances, which, ere the water-spout reach- ed the earth, had been driven upwards, or descending rain-drops and hailstones, must also enter windings, which, however, cross the windings already mentioned ; for movements which are ascending and descending, and which are directed to one and the same side, must cross each other as ab and cd in the accompanying figure. Hence there are generally two spiral movements in a transparent water-spout, one to the right and another to the left. It has been said that water-spouts over water are for the most part transparent, because they contain water; but ex- perience proves, as well as the very nature of the thing, that in the interior there is no connected mass of water. It would be more correct to say that water-spouts which come over the sea are more rarely opaque, because they can contain no dust, and hence can only be so far opaque that they include numerous minute drops, or, what is most usual, a portion of the fog-like cloudy mass. We can, therefore, easily under- stand why the lower part of the middle portion of a water- spout becomes generally transparent at last, viz. because the whirling movement becomes weakened, and the cloud-funnel is hence shortened. We have seen that the air which is immediately above a water-spout, must descend into that portion of it in which the air is attenuated, and, therefore, in the vicinity of the axis more especially. If now, as we suppose, the whirlwind ex- tends upwards, %r above the cloudy mass, in which mere ob- servation would assign its commencement, the descending air, coming from colder regi
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