THE LITERARY 



OF THE LINN^AN ASSOCIATION OF PENNSYLVANIA COLLEGE. 



Vol. if. SEPTEMRER, 1846. No. 11. 



METEOROLOGY. 



PHILOSOPHY OF STORMS. NO. II. 



BY PROF. WASHINGTON L. ATLEE, M. D. PHILADELPHIA, PA. 



In my first number. 1 promised to explain the cause of the barom- 

 eter sinking in the centre of a storm, and continuing to stand low, not- 

 withstanding the wind blows inwards. The difficulty to account for 

 the continued depression of the barometer under these circumstances 

 appeared so great to Sir John Hershel that, in discussing the paper read 

 by Mr. Espy to the Britisli Association at Newcastle, in September 1840, 

 he considered it fatal to this gentleman's theory. The only way Sir 

 John could account for the fall of the barometer was a centrifrugal force 

 in tlie air, arising from the whirlwind character of the storms, as des- 

 cribed by Mr. Redfield and Colonel Reid. Mr. Espy, in reply, called 

 Mr. Hershel's attention to the following statements : Mr. Forth says, in 

 the Philosophical Transactions that, during a great depression of the 

 barometer on the 8th of January, 1735, he observed that the wind in the 

 northern parts of the island blew from the north-east, and on the south- 

 ern parts of the island from the south-west. Mr. Forth adds, that he 

 does not understand why the barometer did not rise above the mean by 

 these two concurrent winds. And Mr. Howard says, in a great storm of 

 1812, the wind, on the north of the Plumber, blew from the East North 

 East, and, on the South of the Humber, from the South West, with sim- 

 ilar results. 



As the barometer stands low, when the atmospheric pressure is di- 

 minished, and high, when it is increased, it must necessarily indicate the 

 least weight in the superincumbent atmosphere immediately over the re- 

 gion in which it stands lowest. There must then be less resistance in 

 this particular region, than in those parts surrounding it where the ele- 

 vation of the barometer is greatest, and, in accordance with the estab- 

 lished laws in Dynamics, there must be a rushing inward of air to where 

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