740 



In examining for seven months the mean ba- 

 rometric height of the days, observed by M. 

 Caldas, I find the least height to be 247.8 11 ; and 

 the greatest 249.0 n . This difference of 1.2 U , or 

 2.7 m , is the effect of small inequalities of diurnal 

 oscillations which accumulate by degrees. It was 

 3.12 mm , in the observations of M. Boussingault. 

 Once only the extent of the variations of the day 

 was but 0.63 nim ; and once only it rose to 3.64 ram . 

 In comparing the observations day by day from 

 9 h in the morning till 4 h in the afternoon, I find 

 that in the observations of M. Caldas, the varia- 

 tions at 9h were from 248.30n to 249.50 11 ; and at 

 4 h from 247.00 11 to 248.66 u ; whence result the 

 differences for 9 h , of 2.7 mm , and for 4 h , 3.6 mm . 

 The labors of M. Boussingault give for those 

 two limit-hours, 4.6 mm and 4.21 min . The limits 

 of the accidental oscillations round the mean 

 of the same hours, were consequently nearly the 

 same at 1365 toises of height, as at the level of 

 the equinoxiai sea; but those extreme limits 

 appear to me to be much more rarely attained 

 on the back of the Cordilleras. The new obser- 

 vations of MM. Rivero and Boussingault, made 

 with excellent barometers of Fortin, furnish the 

 most certain notions hitherto obtained on the 

 laws we have just discussed. They yield, for the 

 mean extent of the oscillations, from 9 h in the 

 morning till 4 h in the afternoon 2.29 mm (re- 

 ducing the barometric heights to the tempera- 

 ture of zero.) 



