STORM

The causes of those violent commotions of the atmosphere to which we give the names of storms, tempests, hurricanes, tornados, , are involved in great obscurity, chiefly from the difficulty of obtaining a precise knowledge of the various circumstances with which they are accompanied. In order to ascertain the general laws of the so phenomena, it would be nece ary to determine, in a great number of particular instances, the place and time at which the storm begins and ends, the path it describes, the extent of atmosphere disturbed, the direction and force of the wind, and the barometic pre ure at every part of the disturbed column during the whole time of its continuance. But several of these points could only be determined from the comparison of a great number of simultaneous observations on that tract of the earth's surface over which the storm pa es; while, from the nature of the thins to be observed,it is evident that a few insulated observations is the most that can be expected in almost any case. Besides, a storm for the most part pa es over some part of the sea, Where, unle a ship unfortunately happens to be caught in it. no observation can be made, or even evidence be obtained of its existence. It is In the torrid zone that storms display the greatest violence, and rage with most destructive fury. In our latitudes they are comparatively rare, and in the polar regions they seldom amount to more than a strong wind. Until recently it was generally believed that during n hurricane the wind, at every part of the agitated ma , blows In a rectilinear and parallel direction, and a storm was considered to be sufficiently explained when it was described as a wind blowing with a/ velocity of 100 or 120 miles in an hour. A comparison of the recorded accounts of the circumstances attending several storms has of late years shown that this idea was erroneous, and that the phenomena are considerably more complicated. Franklin appears to have been the first who remarked that storms travel in a direction opposite to the actual movement of the wind at the time the storm is raging; and he ascribed the phenomenon to a great but partial rarefaction of the air. arising from the sudden precipitation of vapours, or other causes, the consequence of which would nece arily bea simultaneous rush of wind from all quarters to fill up the vacuity: and the ma of air being thus set in motion bya sort of aspiration, the gale will be first felt at those places towards which it blows. (Letters and Papers on Philosophical Subjects.) In a work on winds and monsoons, published in 1801, Colonel Capper was led from a comparison of the details respecting the hurricanes at Pond i cherry and Madras in 1760 and 1773, to remark that these hurricanes must have been whirlwinds, whose diameters could not exceed 120 miles, and that the velocity of the wind at any point was due to the rotatory velocity of the vortex. He also supposed that, besides the gyratory movement which forms the characteristic of the whirlwind, a storm has probably also progre ive motion. Colonel Capper's speculations, however, appear to have met with little attention until the subject was taken up by Mr. Red field of New- York, who, in a series of papers recently published in the American1184 journals, has diligently collected and ex- [s. 1198]