444 SHORT MEMOIRS ON METEOROLOGICAL SUBJECTS. 



At the same time, the cj'clones in the region of the trade winds follow 

 the general movement of the atmosphere in these latitudes from east to 

 west, and similarly in the extropical region they move from west to east. 

 From the resultants of the two constant forces, the polar tendency of the 

 cyclones and the influence of the prevailing movement of the atmos- 

 phere, there result the i)arabolic paths of the cyclones or their recurving 

 when they pass from the trade winds into the region of the west winds. 



Thus far Fereel. 



The influence that a prevailing general current of air exerts upon the 

 progress of a whirlwind that has entered into it evidently consists in 

 this, that the masses of air drawn into the whirlwind have to follow two 

 impulses : one, that which is due to the whirl; and the other, that which 

 is due to their original movements. Therefore, in the region of trade 

 winds and on the northwest side of a whirl, the motions are most accel- 

 erated, but on the opposite side are most retarded, and thereby the 

 wliirl must receive a tendency to progress toward the northwest. I 

 believe that in its principal feature this agrees also with Loioiel's 

 theory of the recurving of the paths of cyclones on their leaving the 

 trade-wind region (see this journal, vol. ix, j). 270). The expression, 

 " Stauung der Luft" sioioing aicay or damming np or hanking iip of the 

 atmosphere, seems to me also not well chosen. I say also, for one of 

 the most competent authorities in the study of the theory of storms 

 writes me in reference to Lommel's views as follows: "I cannot under- 

 stand this theory. The northeast trade does not blow when the cyclone 

 wind prevails. Therefore they cannot bank each other up. It would, 

 however, be interesting to know whether the tropical cyclones have not 

 always a maximum of temperature or aqueous vapor on their right- 

 hand or northeast side. This is an anomaly in the distribution of these 

 elements in the tropical regions, but the cyclones, also, are infrequent 

 phenomena." 



It would certainly be of the highest interest to know the distribution 

 of temperature in the trade- wind region during a cyclone, for this would 

 afford an important test of our storm theories. I believe, however, that 

 the author of the preceding quotation will find fewer difficulties in my 

 presentation of the influence of a general atmospheric current upon a 

 cyclone entering therein. I do not think that everything is explained 

 by this and by Ferrel's " polar tendency," but certainly both views 

 ought to be taken into consideration. 



[Note by the Tra^^slatou.— Having, in 1865-'66, had occasion to personally explain 

 the views of ISIr. Ferrel to several astronomers and meteorologists in Enrope, and hav- 

 ing, in 1869-70, delivered popular expositions of the same subject in connection with 

 the publication of the Daily Weather Bulletin and Forecasts of the Cincinnati Obser- 

 vatory, the author was peculiarly gratified to be able to present these views to a still 

 larger circle by the publication, in May, 1871, of his notes on the use of the tri-daily 

 weather maps of the Signal Service, and would refer American students to the " Monthly 

 Weather Reviews " and other publications of that ofiace for innumerable illustrations of 

 the application of Ferrel's theory. See also the recent publications of Loorais and Fer- 

 rel.— C. A.] 



