

584 Proximate Causes of certain Winds and Storms. 



There is no room for doubt, however, at the present day, that the 

 mean temperature of the part of North America, lying east of the 

 Rocky Mountains, is several degrees lower than that of Europe un- 

 der the same parallels. The paper of Dr. Lovell, in the twelfth 

 Volume of this Journal, is altogether decisive of this point, and, with 

 the results furnished by him, and those obtained by other observers, 

 agree, as might be shown at length, if it were necessary. It ap- 

 pears that in the higher latitudes, as at Stockholden, (lat. 59° 20') 

 in Europe, the mean temperature corresponds to that of a place 

 about 14£° farther south, on the eastern coast of America; in lati- 

 tude 50°, it corresponds to that of a place 8 or 10° farther south. 

 The mean temperature of London, lat. 51° 31', is 49.5 ; that of 

 New Haven, lat. 41° 18', as given by Professor Olmsted, for the 

 years 1827, 1828, is 49.29, and 52.50. About the latitude 30°, 

 the mean temperature becomes nearly the same in both continents. 

 Thus at Grand Cairo and St. Augustine, in latitudes 30° and 29° 

 50', it is 73. and 72.23.* This is an important fact, and accords 

 very accurately with the theory of the cause of these peculiarities 

 that is presently to be stated. 



Two things are therefore to be accounted for — the low mean tem- 

 perature of the eastern part of North America, and the great vicissi- 

 tudes in its temperature. The two are sometimes confounded in the 

 writings that treat of our climate, and sometimes one of them is over- 

 looked or neglected. In remarking on the article of vicissitudes 

 also, we must notice both the wideness of the interval between the 

 general winter and summer range of the thermometer, and those 

 changes which take place within the compass of a few hours. 



The forests by which the whole country was covered when our 

 ancestors landed on these shores, and which have not yet disappear- 

 ed, the immense lakes that occupy its interior, its mountains, the prox- 

 imity of the great northern ocean, its elevation above the bed of the sea, 

 and certain salts supposed to exist in the air, have been by turns as- 

 signed as the causes of the climate of North America. Dr. Halley 

 could account for its extreme coldness in no other way, than by sup- 

 posing that the pole of the world was at some remote period withm 

 the limits of this continent, about Hudson's Bay, and afterwards 

 shifted into its present position, and that this quarter of the globe 

 has not yet acquired the temperature due to its latitude. 



e Dr. Lovcli's tabic. 





