Page:Popular Science Monthly Volume 28.djvu/326

314 reactionary upward movement through the center of the funnel. This center is almost a vacuum surrounded by a cylindrical mass of air of great density and revolving force. Professor William M. Davis, of Harvard College, whose work, entitled "Whirlwinds, Cyclones, and Tornadoes, is well known for its merit and originality, maintains that the destructive power of a tornado is due to the rush of air along the earth's surface toward the vacuum center of the funnel. Some buildings have a stricken, pinched appearance at the top, as if the air had rushed under the edge of a huge cylinder, and swept upward with tremendous power. While it is true that the downward movement predominates, yet the upward movement in the center is equally marked. The iron grip of the tornado-funnel is relieved only by the escape of currents to the upper air through its center, and this again is doubtless due to the decrease of the contrasts of temperature between the opposing currents, thus gradually lessening the air-movement. In the Westwood tornado, when the funnel had gone about a mile northeast of the village, it became thinner, and the distance to the top of the revolving column did not seem more than one hundred feet. As its force still further weakened, it became only a shallow, whirling cloud of débris, six or seven feet above the ground, and about fifty feet in width. These facts present a problem of the relation of air-pressures in which we may look for destructive action m proportion to the height of the column of revolving air.

Lieutenant Finley's interesting studies will soon be of great service to the people. The advancement of the science of meteorology, as well as of other sciences, has always been made through those whose energy in the examination of these subjects has been manifested as an intrinsic liking, regardless of personal gain, a characteristic pointed out long ago by Jean Paul Richter, and reaffirmed by Emerson as the true aim of the scholar. It has been thought that the time will come when greater numbers of men of leisure and means will become steady workers along paths of unprofitable public usefulness. The people look for science to come to their rescue regarding certain evils in politics or in commerce, in over-legislation, in physical and mental life, and in the destruction of life and property by the elements. It does not follow that the service will be rewarded, yet the control or anticipation of any form of destructive action in Nature is a benefit that will live in the annals of the race for many a century.