72 M. Bouvard on the Diurnal 



wise. Modern authors have shrunk from the marvellous 

 character of the phenomena. They either denied the fact it- 

 self, or they disfigured it to render it explicable. They went 

 so far as to make the Trochilos a bird of the size of the thrush, 

 armed with scales and thorns upon its back, and jupon the 

 ends of its wings. Thus in wishing to limit the power and 

 the resources of nature, they were led even to ridicule a truth 

 to which the immediate observation of facts has in our own 

 day conducted us. 



Art. IX. — On the Diurnal Variation of the Barometer at Pa- 

 ris.* By M. Uouvard, Director of the Royal Observatory 

 of Paris, &c. 



Having been favoured by M. Bouvard with a copy of his 

 Memoir, " On the Meteorological Observations made at the 

 Royal Observatory of Paris" which was lately read before the 

 Academy of Sciences, we are enabled to lay before our read- 

 ers an account of some of the interesting results which he has 

 deduced from these observations. 



These observations were not made by M. Arago, as has 

 been generally believed on the authority of Baron Humboldt 

 {Relation Historique, 5 e JLivraison, p. 305,) but by Joseph 

 Marie Bouvard, the brother of our author, and agent to the 

 Board of Longitude, who since 1808 has been specially charg- 

 ed with the meteorological observations at the Royal Observa- 

 tory. 



The length of M. Bouvard's memoir will not permit us to 

 follow him very minutely in his inquiry ; but we shall endea- 

 vour to extract the most valuable of his results. 



" It has been long known," says M. Bouvard, " that the ba- 

 rometer experiences, in our climate as well as at the equator, a 

 periodical daily variation, which becomes sensible when a suf- 

 ficient number of observations are combined, in order to com- 

 pensate the fortuitous effects of accidental causes. A single 

 month is sufficient to exhibit it ; and it may thus be found 

 that it attains its greatest elevation at 9 h a. m., and then falls 



• See this Journal, No. iv., p. 336 ; viii., p. 290; xv., p. 113 ; and xvi., 

 p. 218. 



