HOW THE WIND BLOWS

Dominion, Volume 12, Issue 175, 19 April 1919, Page 8

HOW THE WIND BLOWS

A GREAT MYSTERY Of alt the familiar subjects which have interested and exercised the minds of men through the ages, it is curious that the most familiar of all should lie. the one which proved lo be the most baffling in any attempt to explain it (says a writer in the "Mornijig Post"). Through thousands cf ''ears the wind was regarded as some irresponsible demon residing in a cave, and who divided his timo between sleeping and displays of uncontrollable violence. We hau; if on the highest authorities that, nineteen centuries ago it was not known whence tho wind came or whither it went, and this was true down until the close of the eighteenth century, in spile of many attempts to solve the problem. Philosophers could do ho more than admit that ''the wind had blown out the candle of reason and left them all in tho dark." The first) ray of hope was announced in tho year 1801, when Colonel Caliper, of the East India Service, put forward the theory that storms were really greatwind systems having a gyratory' movement. The idea .seemed too good to be true, and the subject dropped. In 1821 an- American naval architect, Redfield, noted how the trees which had been blown down during tho passage of a storm formed a regular .curve in the directions in which they lay, and he became convinced that the storm was of a rotatory character. Fearing if he announced his belief that his only reward would be ridicule, he tided his time until another storm supplied him with confirmatory evidence, and in "Silliman's Journal" for April, IS.II, he published n paper demonstrating tlio whirling and progressive character of storms. Keen discussion arose out cf the discovery, some holding that the wind blew along a straight course, others that it made a true circle. The controversy was maintained through many years, but in 18-18 Piddington proposed to describe a storiii wind as a cyclone, from a Greek word signifying incurving, like tho coil of a snake, so that it would mean neither a straight line nor ;; perfect' circle. For years after this- investigators concentrated their energies on stormfields, not suspecting that there was anything worthy of attention beyond the limits of the galo. In the. Northern Hemisphere not a single instance had been met with of storm wind revolving other than against clock hands, a. fact which was of enormous benefit, especially lo seamen.

From Cyclones te. Anti-Cyclon s. About 1860 tho late Sir Francis Cuilton extended Hie investigation to all winds, whether gales or not, and to everybody's surprise it was discovered that beyond the stormfields they were extensive regions over which tho quieter winds re-; volved in a direction with clock hands. On the face of it this was a lint contradiction of the cyclonic view, but the mystery was soon solved when it was seen that the cyelono formed <111 area in which vtho bjrometbr readings were lower, often very, inuqh lower, than tuose in the reversed wind system lying outside. Sir Francis Gallon, finding I hat the barometer, tho wind, tho weather, ami other elements were the opposite of those in a cyclone, adopted for the new system the name anticyclone. AVhen the whole question was submitted to examination it was evident that there wore numbers of both cyclones rind anti-cyclon?s moving hither and thither over the earth's ' surface every div. and that I lie one type cannot exist without the other. Tho anti-cyclone, bifing a region of the heaviest atmosphere, wc may regard as tho reservoir which supplies the cyclone, where- the ait is at its lightest, and, as was shown in tho explanation of Millibars, the. energy of the cyclone depends upon tho steepness of the pressure gradient bohvcen the hn;!i and low areas. Altl'oug'i the wind circulates in one direction in tlio cyclone and in the oposito direction in the anti-cyclone the law whk'li reunlatm the relation of the wind to 'he pressure is the same in both cases. The knowledge of this law has served to save Heels of ships) and their, crews. It is very simple: Face the wind and the lowest barometer is away lo the right and the highest to the left. This is true in all circumstances in the Northern Hemisphere, the conditions l-eing reversed beyond' the Equator,