392 THE POPULAR SCIENCE MONTHLY. 



higher latitudes such was the simplest expression of Dove's the- 

 ory given in text-books.* 



Under this provisory hypothesis meteorology made an im- 

 mense progress, and some five-and-thirty years ago, Leverrier in 

 France, and Fitzroy in England, ventured for the first time to 

 foretell weather twenty-four hours in advance, or at least to send 

 out warnings as to the coming storms. This bold step brought 

 meteorologists face to face with a quite new problem. From the 

 air pressure, the temperature, the moisture, and the winds ob- 

 served at a certain hour of the day at various spots and tele- 

 graphed to a central station, they had to infer the next probable 

 state of weather. So, leaving aside the great problems of atmos- 

 pheric circulation, they directed their attention to the changes of 

 weather rather than to the causes of the changes, f For this pur- 

 pose purely empirical laws were of great value. When the me- 

 teorologist saw on a weather chart a region of low atmospheric 

 pressure, with winds blowing in spirals round and toward its 

 center, he named it, by analogy with real cyclones, a " cyclonic 

 disturbance " or a " cyclone," giving the name of " anticyclone " 

 to the region of high atmospheric pressure and he studied the 

 tracks of both disturbances in their advance across the oceans and 

 the continents. He did not inquire for the moment into the causes 

 of the disturbances ; he took them as facts, and, following Buys 

 Ballot's law, he said that the wind will blow as a rule from the 

 region of high barometic pressure (the anticyclone) to the region 

 of low pressure (the cyclone), with a certain deflection to the right 

 or to the left. Immense researches were made to study the routes 

 followed by the centers of barometrical minima, and we now have 

 splendid atlases showing the normal tracks of cyclones across the 

 Atlantic Ocean, over Europe and the States, in Japan, in the In- 

 dian Ocean, and so on, at various seasons of the year.J With these 

 empirical data meteorologists attained such a perfection in their 

 weather forecasts that in five cases out of six their previsions are 

 now correct, while the coming gales are even foretold with a still 

 greater accuracy. 



*E. E.'Schmid, Lehrbuch der Meteorologie, Leipsic, 1860, p. 568. 



f See W. Bezold's short sketch of meteorological progress in Sitzungsberichte der Ber- 

 liner Akademie der Wissenschaften, 1890, ii, 1295, sq. 



\ Besides the earlier works of Ley (Laws of the Winds prevailing in Western Europe, 

 Part I, 1872) and Koppen (Wissenschaftliche Ergebnisse aus der monatlichen Uebersichten 

 des Wetters, l73-'78), we have now the splendid work of W. J. Van Bebber, which em- 

 bodies the tracks of all cyclones in Europe for the last fifteen years (Die Zugstrassen der 

 barometrischen Minima, fiir 1875-'90), the researches of Blanford, S. E. Hill, and Elliot in 

 the Indian Meteorological Memoirs and Cyclone Memoirs, Part IV (published by the Mete- 

 orological Department of India), the work of E. Knipping for Japan, in Annual Meteoro- 

 logical Report for 1890, Part II, Appendix, and several excellent works for Russia. 



