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. 
Tt 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 (1 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. 
