750 



for that reason, is less violently agitated than in 

 the northern hemisphere. 



Almost on the parallel of the Havannah, but 

 164° more to the west, at Canton and Macao in 

 China, the extent of the horary oscillations 

 presents nearly the same constant equality: 

 the mean of the months differ* 7| millimeters; 

 but the greatest variation observed during a 

 whole year on the same day, (January 15th 

 1814), was only 4 millimeters. 



At Cairo, where (as in the Canary Islands) % 

 the mean horary variations do not rise above 

 0.5" or 0.8 U (1.10 mm or 1.76 mm ), the extreme 

 variations are inconsiderable, and scarcely dif- 

 fer from those which M. Dorta observed at Rio 

 Janeiro. M. Cou telle saw the column of mer- 

 cury vary only 22 millimeters in the course of 

 three years, from the effect of accidental pertur- 

 bations. These limits of perturbation approach 



• I find from the manuscript journal of the M. l'abbe 

 Richenet, the mean of the twelve months of the year 1814, 

 at Macao, as follows : 30.34 in (th. 680 Fahr.) 5 30.30 (th. 

 65°) ; 30.26 (th. 66°) j 30.11 (th. 71°) 5 30.11 (th. 74°) 5 

 29.96 (th. 81°) } 29.99 (th. 83°) ; 29.99 (th. 83«) ; 30,15 

 (th. 80°) ; 30.19 (th. 78°) ; 30.28 (th. 72°) ; 30.35 (th. 82°). 

 Mean of the year 30.17 in (th. 74°). The scale is in English 

 inches. The barometric heights are not reduced to the tem- 

 perature of zero. 



t At Cairo, January 3rd 342.0 n (th. 5.5° R.) ; January 

 16th, 335.5" (th. 10). Difference reduced to the tempera- 

 ture of zero, 15.41mm. 



