Wind

(wind or wind.) [A. S.] (Meteor.) The movement of the air in currents from one place to another. Speaking generally, all winds are caused by the variations taking place continually in the condition of the air as respects heat and moisture, and therefore as respects rarity. When the air over a given place becomes rarefied, that is, when the atmospheric pre ure there becomes relatively small, that region at once becomes a centre towards which inflowing air-currents direct themselves. According to the nature, extent, and continuance of this diminution of pre ure, the nature of the resulting air - currents varies within very wide limits. See TRADE WINDS, ATMOSPHERE, & c.-The causes which produce storms, tempests, hurricanes, ., are very obscure. It is difficult to arrive at general laws regarding them, since it is not easy to obtain an exact knowledge of the various circumstances which accompany them. Storms are violent and destructive in the torrid zone; they are comparatively insignificant in temperate, and are scarcely known in polar regions. Itwas formerly supposed that a storm was merely a wind blowing in a certain direction at the rate of 100 or 120 miles an hour; but it has been recently found to be far more complicated in its nature. There is reason to believe that, in the northern hemisphere, the great body of the storm whirls in an horizontal circuit round a vertical or somewhat inclined axis of rotation which is carried forward with it; and that to a spectator placed in the centre the rotation is always from right to left. Storms travel in a direction differing from the actual movement of the wind at the time. When the storm progre es westward the wind, at the commencement, is from a northern quarter, and towards the end from a southern. When the progre ive motion is eastward, the phenomena are reversed; southern storms are subject to the same modification as northern, but in a reversed order. In all latitudes, the barometer sinks during the first half of the storm, in every part of its track; and rises during the second. It is a erted by some that in storms the tendency of the wind is from all round to some centre of central line, and there maybe storms having this character also. Were the phenomena of storms well understood, the navigator might avoid the tracks in which they prevail at particular times; or, being caught by one, might steer the [s. 963]