232 M. Arago's Historical Eloge of Joseph Fourier, 



complished. The fearful congelation of the globe, whose 

 epoch was fixed by Bnffon at the instant the central heat shall 

 be totally dissipated, is thus a mere dream. At the surface, 

 the earth is affected only by solar heat. • So long as the sun 

 shall retain the same brightness, the human race, from pole to 

 pole, will find in every latitude the climates which allowed 

 them to settle and live there. 



These, gentlemen, are great and magnificent results. In re- 

 cording them in the annals of science, historians will not ne- 

 glect to mention this singular peculiarity, that the geometrician 

 to whom we owed the first certain demonstration of the exist- 

 ence, in the interior of our globe, of a heat independent of the 

 solar influence, has reduced to nothing the immense share 

 which was attributed to this original heat, in the explanation 

 of the phenomena of terrestrial temperature. 



To the merit of having freed the theory of climates from 

 an error which had kept its ground from being supported by 

 the imposing authority of Mairan, Bailly, and Biiffbn, Fourier 

 added the still greater merit d( introducing into this theory, a 

 consideration totally neglected before his time : he remarked 

 the influence which must be exercised by the temperature of 

 those celestial spaces^ amidst which the earth describes its im- 

 mense revolution round the sun. 



On seeing, even at the equator, certain mountains covered 

 with eternal snow, and on observing the rapid decrease of tem- 

 perature in the strata of the atmosphere during ascents by the 

 balloon, meteorologists had supposed that excessive cold must 

 prevail in the regions which, from the extreme rarity of the 

 air, will always be unapproachable by man, and especially in 

 those beyond the limits of our atmosphere. It was not merely 

 by hundreds, but by thousands of degrees that they would 

 have measured it. 



However, as usual, the imagination had passed all bounds. 

 The hundreds and thousands o^ degrees became, after the 

 strict examination of Fourier, only fifty or sixty degrees. Fifty 

 or sixty degrees below zero is the temperature maintained by 

 stellular radiation in the unbounded spaces traversed by the 

 planets of our system. 



You all recollect, gentlemen, how fond Fourier was of expa-. 



