SHORT MEMOIRS ON METEOROLOGICAL SUBJECTS. 423 



States for 1872 and 1873 with special reference to storms. The paths 

 of the storms during 314 days were examined ; the mean direction of 

 their progress was very nearly from west to east.^ "One circumstance 

 seems to have a decided influence upon the modifications of the storm- 

 paths — this is the rainfall. Every considerable barometric depression 

 is accompanied by rainfall, and the area over which the rain occurs 

 generally extends much farther on the eastern or forward side of the 

 central depression tban on the western." And the farther the rain-area 

 stretches on the east side of the storm, so much the more rapidly does 

 the storm advance in this direction. By separating the cases in which 

 the storm-track had a direction more to the north or south, Loomis 

 further found that the direction of the storm-path in 24 hours very 

 nearly agreed with that toward which, in the preceding eight liours, the 

 rain-area had extended the farthest. If the greater axis of the region 

 of rain was directed toward N. 53° E. or N. 118° E., then the mean 

 direction of the corresponding storm-tracks was i!s^. 40° E. or N. 116° E. 

 " The agreement would certainly have been still greater if we could have 

 made the comparison with the direction of the storm-tracks in the next 

 8 hours instead of 24." 



Since the beginning of 18G7, in the Norwegian Meteorological Insti- 

 tute, the most important meteorological observations at 210 European 

 stations have been, day by day, graphically presented upon a chart. By 

 these charts, Mohn establishes the fact that on the front or east side of 

 the storms the tension of the vapor and the quantity of cloudiness in- 

 creases, and that there heavier and longer continued rain or snow pre- 

 vails ; on the hinder or western half, however, the vapor-tension falls, 

 the cloudiness diminishes, and the rain is light. 



The barometric minima of the Torrid Zone are regularly accompanied 

 by the heaviest rains, and, according to Thom,^ the condensation of vapor 

 stretches much farther on the front than on the hinder side of the cyclone. 

 The island of Mauritius, to which numerous vessels repair after every 

 great storm, afforded for many years a very favorable position for the 

 study of tropical whirlwinds to Thom and to its meteorological society, 

 still flourishing under Meldrum's guidance. Thom explicitly says that no 

 phenomenon accompanies these storms so regularly and is so astonish- 

 ing as the enormous mass of water falling from the moving masses of 

 air. "Hundreds of miles distant, on all sides of the whirlwind, extends 

 a thick stratum of clouds that pours out rain in torrents and unceas- 

 ingly. This process continues week after week, and is apparently char- 

 acteristic of a hurricane in all its stages. The approach of such a storm 

 can almost be predicted from the unbroken layer of clouds that slowly 

 covers over the heavens, at first at a great altitude, gradually, however, 

 descending to the lower strata and accompanied by increasing darkness, 



■'• Loomis. See Zeitschrift, Bd. i, pp. 245--251, and American Jonrnal of Science, lb74. 

 t Thom, Au Inquiry into the Nature and Course of Storms in the Indian Ocean, South 

 of the Equator. London, 1H4.">. pp. 202, 200. 



