HOW WIND PRODUCES WAVES.

Ashburton Guardian, Volume XXIX, Issue 7830, 24 June 1909, Page 4

HOW WIND PRODUCES WAVES.

There are wind waves m water, sand and snow. The great sea waves are produced at that part of a cyclone where the diretion of the wind coincides with the direction of advance of the depression. Along this line of advance the waves m their progress are accompanied by a strong wind blowing across their ridges as long as the atmospheric depression is maintained. So the waves are developed until they become steep. The average height m feet is about half the velocity of the wind m miles. A wind of fifty-two miles an hour gives waves of an averago height of twenty-six feet, although I individual waves will attain a height of forty feet. The prevailing wind m all longtitucles is westerly, so wherever a westerly wind springs up it finds a long westerly swell, the effect of a previous wind still running, and the principal effect of the newly-born wind is to increase the steermess of the already running long swell so as to form majestic storm waves, which sometimes attain a length of 1200 feet from crest Ito crest. The longest swells due to wind are almost invisible during storms for they are masked by the shorter and steeper waves, but they emerge into view after or beyond the storni, The action of the. wind to drift dry sand m a procession of waves is seen m the deserts. As the sand waves cannot travel by gravitation their movements are entirely controlled by the wind, and they are therefore much simpler and moro regular m form and movement than ocean waves. In their greatest heights of several hundred feet the' former become more complex owing to tht» partial consolidation of the lower layers of sand by pressure, but they still have the characteristic wave features. In the Winnipeg prairies of Canada freshly fallen snow is drifted by wind m a procession of regular waves progressing with a visible and ghostlike motion. They are similar to desert sand waves, but less. $lian half as steep, the wave length Ijeiiig rifty times, as grout ?»_8 tho' height. The. flatness of the wind-formed snow waves affords a valuable indication of i the great distance to which hills sjieltov from the wind, j