388 HEINRICH WILHELM DOVE. 



changes. He discussed particularly the non-periodical changes of 

 temperature, and published his conclusions at five different times be- 

 tween the years 1838 and 1852 in the Abhandlungen of the Berlin 

 Academy. He divided the year into seventy-three periods, each live 

 days in length, and computed the mean temperature of every one of 

 them, — a method which was indorsed by the first international con- 

 gress of meteorologists in 1873. He exploded the notion that the 

 late frosts between the 11th and 13th of May, from which the or- 

 angery of Frederick the Great at Sans Souci did not escape, had any 

 wide significance. Though popular tradition associated them with 

 the death or martyrdom of Mamertus, Pancratius, and Servatius, and 

 assigned to them a cosmical origin, the phenomenon was strictly local, 

 and was explained, where it occurred, by the reflex action of a cold 

 district in the neighborhood. 



Brandes first broached, in 1820, his centripetal theory of storms, as 

 the result of his study of the weather of 1783. In 1826, he pub- 

 lished what he regarded as a confirmation of his views, deduced from 

 the great storm of December 24, 1821. In 1828, Dove re-examined 

 the data which had led Brandes to his conclusion, and maintained that 

 the latter storm was a true whirlwind, revolving against the motion of 

 the hands of a watch, while the storms of the southern hemisphere, 

 which he had investigated, revolved in the opposite direction. Before 

 Dove resumed the subject, Redfield and Reid on the one hand, and 

 Espy on the other, had been engaged in an animated discussion on 

 the merits of the centrifugal and centripetal theories as exemplified 

 in the storms of the Atlantic, the hurricanes of the West Indies, and 

 the typhoons of the Chinese Sea. Dove generously admits, with a 

 candor not always found in scientific men, that Redfield and Reid had 

 reached their conclusions without the aid or knowledge of his own 

 earlier publications on the subject, and he credits them for their rich 

 materials and their independent generalizations, in his " Law of 

 Storms," published in 1841. He says: "But Redfield and Reid, 

 besides placing on a wider basis the rotary movement, which takes 

 place in opposite senses in the two hemispheres, have added, farther, 

 some very important observations, the empirical establishment of which 

 is entirely their own ; these I shall attempt to connect theoretically 

 with the cyclone movement." He then proceeds to show that the 

 larger whirlwinds, and their opposite characters north and south of 

 the. equator, may be evolved from Hadley's general theory of the 

 trade-winds and the transfer of air across parallels of different mag- 

 nitudes ; admitting at the same time that lesser whirls of air and 



