COSMOGONIC SPECULATIONS OF DESCARTES. 423 



were to suppose that each of you had not deduced from 

 these remarkable facts a conclusion no less remarkable, 

 to which indeed the fossil flora had already habituated 

 us ; namely, that as they have grown older, the polar 

 regions of the earth have cooled down to a prodigious 

 extent. 



In the explanation of so curious a phenomenon, cos- 

 mologists have not taken into account the existence of 

 possible variations of the intensity of the solar heat ; and 

 yet the stars, those distant suns, have not the constant 

 brightness which the common people attribute to them. 

 Nay, some of them have been observed to diminish in a 

 sufficiently short space of time to the hundredth part of 

 their original brightness ; and several have even totally 

 disappeared. They have preferred to attribute every 

 thing to an internal or primitive heat with which the 

 earth was at some former epoch impregnated, and which 

 is gradually being dissipated in space. 



Upon this hypothesis the inhabitants of the polar re- 

 gions, although deprived of the sight of the sun for whole 

 months together, must have evidently enjoyed, at very 

 ancient epochs, a temperature equal to that of the trop- 

 ical regions, wherein exist elephants in the present 

 day. 



It is not, however, as an explanation of the existence 

 of elephants in Siberia, that the idea of the intrinsic heat 

 of the globe has entered for the first time into science. 

 Some savans had adopted it before the discovery of those 

 fossil animals. Thus, Descartes was of opinion that orig- 

 inally (I cite his own words,) the earth did not differ 

 from the sun in any other respect than in being smaller. 

 Upon this hypothesis, then, it ought to be considered as 

 an extinct sun. 



