752 



these quantities differ from single * to double." 

 M. Arago, whose meteorological observations 

 already comprehend 9 years, and who disposed 

 them in such a manner as to place most in 

 evidence the value of the diurnal variation 

 of the barometer, finds, that the descending 

 oscillation at Paris, from 9 h in the morning till 

 3 U in the afternoon, is only 0.8 ram (0.35 u ) ; and 

 that in reducing all the heights to the same 

 temperature, the mean of 15 to 20 days suf- 

 fices, at all seasons, to ascertain the existence 

 and movement of the horary oscillations J, 

 We have se^n that the mean of the barometric 



* According to my first view, the type of the movement 

 of the barometer, on the shore of the equinoctial sea, ap- 

 peared to me as follows : the mean barometric height at 

 8 h in the morning, will give, h + 0.5 1 *; at 4 h in the after- 

 noon, h — 0.4!* 3 at ll h at night, h -f 0.1 li \ at 4 h in the 

 morning, h — 0.21*. It results from this hypothesis, for 

 9^ in the morning, 338.30" ; for noon, 338.02" \ for 4 h in 

 in the afternoon, 337.40" j for ll h at night, 337.91" \ for 

 4 h in the morning 337.60". See my Essay on the Geogr. 

 of Plants, p. 91, and my Rec. d'Obs. astr. } vol. i, p. 286, 

 289. 



t See the important discussions in the Annales de chimie et 

 de physique, Vol. iii, p. 442 ; Vol. vi, p. 439 j Vol. ix, p. 426; 

 Vol. xii, p. 421 j Vol. xv, p. 416 j Vol. xviii, p. 407. 



J It is to be regretted that the observations at Paris and 

 Geneva cannot be compared, the latter containing no ele- 

 ment that serves to make known the horary observations. 

 (L. c, Vol. vi,p. 440). 



