I 



753 



heights of the months, differs 1.2 mm , near the 

 equator, and 8 mn V near the tropics of cancer and 

 Capricorn (at Rio Janeiro and the Havannah). 

 At Paris (iat. 48° 50') the monthly mean gene- 

 rally varies from 8 to 9 millimeters* in one 

 year. The compensation of these accidental 

 variations is such, that at the center of tem- 

 perate Europe, one month suffices to approach 

 at least \ nearer the mean value of the baro- 

 metric heights, than that which we find on 

 the confines of the equinoctial and temperate 

 zone \. 



M. Marque* Victor found at Toulouse (lat. 

 43° 35 ; ) the mean of the extent of the horary 

 oscillations, 1.2 mm ; he remarked no connection 



* I wish I could compare Paris with some spot placed in 

 the same latitude, on the eastern coast of America ; but we 

 have hitherto no precise observations on the horary varia- 

 tions of the barometer, except those which an observer full 

 of zeal, M. Jules Wallenstein, has lately made at Washing- 

 ton (lat 38° 55'), where the mean temperature (14.7° cent.) 

 is 4 degrees above the mean temperature of Paris. The 

 barometric heights of the different months varied at Wash- 

 ington in 1824, 14.8 mm , or 6£ lines ; which proves how 

 much the atmosphere is subject to great variations, on the 

 eastern coast of the United States. {Amer. Trans., 1824, 

 p. 7). 



f In some years it has happened that the barometric 

 mean of the months has differed less at Paris than .at Rio 

 Janeiro, and the Havannah. This difference was only from 

 51 to 6i millimeters, in 1816 and 1819, 



VOL. VI. 3 D 



