NOTES. XC1X 



Boussingault's " Econ. rurale," T. i. pp. 53 68 ; and Liebig's " Organische 

 Cliemie," S. 16 and 21. 



t 330 ) p. 307. Gay-Lussac, in the " Annales de Chimie," T. liii. p. 120 ; 

 Payen, " Mem. sur la composition chimique des Vegetaux," pp. 36 and 42 ; 

 Liebig, " Org. Chemie," S. 299345 ; Boussingault, " Econ. rurale," T. i. 

 pp. 142153. 



( 381 ) p. 307. By applying the formulae which Laplace communicated to 

 the Board of Longitude a short time before his death, Bouvard found, in 1827, 

 that the portion of the horary oscillations of the pressure of the atmosphere 

 which results from the attraction of the moon, cannot raise the column of 

 mercury in the barometer at Paris more than 0'018 of a millimetre; while 

 the mean oscillation of the barometer, derived from 11 years' observation at 

 Paris, is 0'756 of a millimetre from 9 A.M. to 3 P.M., and 0'373 of a milli- 

 metre from 3 P.M. to 9 P.M. See " Me'moires de 1'Acad. des Sciences," T. vii. 

 1827, p. 267. [The hourly observations made since 1842 at the British 

 Magnetical and .Meteorological Observatory at St. Helena, have shewn that 

 the attraction of the moon causes the mercury in the barometer to stand, on 

 the average, '004 of an English inch higher when the moon is on the 

 meridian above or below the pole, than when she is six hours distant from 

 the meridian. (Phil. Trans. 1847, Art. V.) EDITOR.] 



(S 82 ) p. 308. Observations faites pour coustater la marche des variations 

 horaires du barometre sous les tropiques, in my Relation historique du Voyage 

 aux Regions Equinoxiales, T. iii. pp. 270 313. 



[The impulse and systematic direction which has been given to meteoro- 

 logical observations, by the establishment of meteorological observatories in 

 different parts of the globe, has already thrown a new light on the diurnal 

 variations of the barometer. It has become known that at stations situated 

 in the interior of great continents, very distant from the ocean or from large 

 bodies of water from whence supplies of aqueous vapour may be derived, and 

 where the air consequently is at all times extremely dry, the double maxi- 

 mum and minimum of the diurnal variation of the barometer either wholly or 

 almost wholly disappear, and the variation consists in a single maximum and 

 minimum, which occur respectively nearly at the coldest and at the hottest 

 hours of the day ; the greatest height of the mercury being at or near the 

 coldest hour, and the least height at or near the warmest hour. For this 

 simple state of the phenomenon an equally simple explanation presents itself: 

 the surface of the earth becoming warmed by the sun's rays, imparts heat to 

 the strata of the atmosphere in contact with it ; the superincumbent air thus 



