PRIMITIVE HEAT OF THE EARTH. 429 



the stars has established in the regions furrowed indefi- 

 nitely by the planets of our system. 



You recollect, Gentlemen, with what delight Fourier 

 used to converse on this subject. You know well that he 

 thought himself sure of having assigned the temperature 

 of space within eight or ten degrees. By what fatality 

 has it happened that the memoir, wherein no doubt our 

 colleague had recorded all the elements of that important 

 determination, is not to be found ? May that irreparable 

 loss prove at least to so many observers, that instead of 

 pursuing obstinately an ideal perfection, which it is not 

 allotted to man to attain, they will act wisely in placing 

 the public, as soon as possible, in the confidence of their 

 labours. 



I should have yet a long course to pursue, if, after 

 having pointed out some of those problems of which the 

 condition of science enabled our learned colleague to give 

 numerical solutions, I were to analyze all those which, 

 still enveloped in general formulae, await merely the data 

 of experience to assume a place among the most curious 

 acquisitions of modern physics. Time, which is not at 

 my disposal, precludes me from dwelling upon such devel- 

 opments. I should be guilty, however, of an unpardon- 

 able omission, if I did not state that, among the formula 

 of Fourier, there is one which serves to assign the value 

 of the secular cooling of the earth, and in which there is 

 involved the number of centuries which have elapsed 

 since the origin of this cooling. The question of the an- 

 tiquity of the earth, including even the period of incan- 

 descence, which has been so keenly discussed, is thus 

 reduced to a thermometric determination. Unfortunately 

 this point of theory is subject to serious difficulties. Be- 

 sides, the thermometric determination, in consequence of 

 its excessive smallness, must be reserved for future ages. 



