Page:Popular Science Monthly Volume 43.djvu/411

Rh exciting just now a great deal of interest, has openly broken with the old theory as regards the origin of cyclones and anticyclones. From observations made for several years in succession on the top of the Sonnblick—a peak twelve thousand feet high, of the Tyrolese Alps—as well as from observations made on several high-level stations, he has concluded that a cyclone can not be due to a local heating of the earth's surface and to an ascending current of warm air provoked by this cause, just as an anticyclone can not be due to a local cooling of the earth's surface, and to a consequent condensation of the air. Contrary to the previsions of the meteorologists, the ascending column of air within a cyclone, up to a height of some ten thousand feet, is not warmer than the surrounding air; it is cooler within the cyclone, and its upward motion thus can not be due to its temperature. So also in an anticyclone the descending current of air is warmer than it is under normal conditions, and its downward motion must be due to some other cause than an increase of density resulting from a lowering of its temperature. The decrease of pressure in the one case, and its increase in the other, thus can not be caused by differences of heating or cooling of the lower strata; and both cyclones and anticyclones must be considered as parts of the general circulation of the atmosphere, such as it was conceived by Ferrel.

Such a deep modification of the current views, though supported to a great extent by weighty evidence, will obviously not be accepted without opposition; but it is already making its way, and certainly will exercise a deep influence on the further development of meteorology.

Abandoning now the domain of theoretical investigation, I must mention a work—also a life's work—which may safely be placed side by side with the best achievements in theory. I mean the beautiful charts of Mr. Buchan, representing the distribution of pressure, temperature, and winds over the surface of the globe, embodied in the last volume of the Challenger Expedition Reports. When Mr. Buchan published twenty-three years ago his first maps of monthly isobars and prevailing winds, they were quite a revelation, even though the data upon which they were based were very incomplete at that time. But better data have