Show HURRICANES BY N S SHALER In tin season of hot weather in the central part of the Mississippi Valley there often come succession of days when the ulmospbsre id not stirred by the winds but remains as still as the air of a cave Despite the steady gain in tho heat the sky stays oloud leas or at most is flocked by those light clouds that lie five miles or more above the surface of the earth All nature seems cowed beneath the fervent fer-vent heat yet there ia nothing of distinct portent in earth or air At last towards evening there may be seen a sudden curdling of the western sky in a few minutes the clouds gather earning from nowhere grow ng at once in the lurid air In lees than half an hour the forces of the storm are organized and its dreadful advance begins If WB were just beneath be-neath th3 gathering clouds we should find that the air over a space a mile or so in diameter was epining around in a whirlpool and while the revolving revolv-ing mifta slowly advanced tbe central part moved rapidly upward Beginning ginning slowly ail the movement of the corm the whirling action the vertical streaming of tue air its onward on-ward movement nil gain speed of motion with astonishing rapidity In a minute or two some cubic miles of air are in a state of intense gyratory movement moving upwards as violently len ly as the gases over a volcano To I replace this strong whirling uprusb theri is an indraught from every side towards tbe centre of the wirlwind and as this centre moves quickly forward for-ward the rush of air is btrongest from behind towards the advancing hurricane I hurri-cane The rate at which the storm goes forward s very variable though it is generally as much as forty to one hundred nailed an hour but this is not tbe measure of its destructive power The raiding effect of the storm ia much greater than would be given by a simple blast of air moving at this speed Much of this peculiar capacity fpr destruction msy perhaps be due the to gyratory motion of the wind in tne storm centre which on one side of the whirlwind adds the speed arising from its circular cir-cular movement to the tranelatory velosity of tUB whirlwind itself Some of the records tell us that houses with closed windowa have been known to burst apart as if from an explosion of gunpowder while others that had their doors and windows wide open remained essentially unharmed It has been conjectured that this action may be due to a sudden rarefaction of the air on the outside of the building build-ing but this oauae cannot be sufficient suffici-ent to produce such tfieuta and if such explosions occur the cause must be looked for elsewhere After the storm id once developed it seems very quickly to arqaira ita maximum of destructive power and its speed of translation At the outset and during dur-ing the period of most efficient action the strip of country affected is generally gener-ally very narrow not often exceeding a mile in width as the storm advances ad-vances the path seems gradually to grow wider and the gyratory movement move-ment aa well as the tranalatory motion of the meteor leas considerable until at last it fades into an ordinary thunderstorm i thun-derstorm or diet into calm March Atlantic |