78 M. Bouvard on the influence of the Wind, fyc. 



evident also that the daily period is almost nothing from ob- 

 servations influenced by the south winds ; that it is very great 

 under the north-west and east winds; and that the mean is 

 nearly equal to that which was deduced from the whole obser- 

 vations of eleven years, as given in a former paper, (p. 72.) 

 In whatever way, therefore, we combine the observations, the 

 daily period subsists, and always shows itself nearly with the 

 same value. 



If we unite the observations at different hours when under 

 the influence of the same winds, we shall obtain the following 

 results : — 



Number of Height of the 



Winds. Observations. Barometer. 



m 



South, - 2029 - 752,75? 



South- West, - 2125 - 753,227 



West, - 2606 - 755,950 



North- West, - 1056 - 758,412 



North, - 1470 - 759,776 



North-East, - 1142 . 759,672 



East, - 958 - 757,221 



South-East, - 658 - 754,300 



12044 756,414 



This table shows in the clearest manner the influence of the 

 wind on the heights of the mercury in the barometer. The 

 smallest height corresponds to the south wind, and the greatest 

 to the north wind. The difference is 7 m .019. M. Burck- 

 hardt, by means of the observations of Messier, found the same 

 difference to be 5 ra .146. — Connoissance des Temps, 1805, p. 345. 

 If we take a mean term between the heights which corre- 

 spond to opposite winds we shall obtain results which are nearly 

 equal. 



m 



Mean of the/- South and north, - 756,267 



heights which ) South-west and north-east, 756,450 



correspond to) West and east, - 756,585 



winds of ^ North-west and south-east, 756,356 



Hence we may conclude, that, in order to determine exactly 



the mean height of the barometer, we should, in our climate, 



employ as much as possible an equal number of observations 



made during winds of opposite directions. 



