Temperature of the Terrestrial Globe. 19 



transparency of the waters appears to concur with that of the air in 

 augmenting the degree of heat already acquired, because luminous 

 heat flowing in, penetrates, with little difficulty, the interior of the 

 mass, and non-luminous heat has more difficulty in finding its way 

 out in a contrary direction. 



The succession of the seasons is maintained by an immense quan- 

 tity of solar heat, which oscillates in the crust of the earth, passing 

 below the surface during one half of the year, and returning into the 

 air in the other half. Nothing can contribute more to throw light upon 

 this part of the inquiry than the experiments, the object of which 

 is, to measure with precision the effects of the solar rays upon the 

 earth's surface. For this reason, we heard with the greatest interest 

 the reading of the memoir presented by Prof. Pouillet ; and if in 

 the course of this article we have not mentioned his experimental 

 researches, it is simply from the wish not to anticipate the report 

 which will soon be made. 



1 have united in this article all the principal elements of the analy- 

 sis of terrestrial temperature. It is made up from the results of my 

 researches long since given to the public. When I began the inves- 

 tigation of such questions there existed no mathematical theory of 

 heat, and we might well have doubted that such a theory could be 

 possible. Those memoirs and treatises in which I have established 

 this theory, and which contain the exact solution of the fundamen- 

 tal questions, have been submitted and publicly read, or printed and 

 analyzed in the " Mecueils Scientijiques,^' of the last few years. The 

 object of this last article is to invite attention to one of the most im- 

 portant questions of natural philosophy, and to present general views 

 and results. It would be impossible to resolve all doubts connected 

 with a subject so extensive ; which comprises, besides the results of 

 a new and different analysis, physical considerations very varied in 

 their natures. Exact observations will hereafter be multiplied. The 

 laws on which depends the motion of heat in liquids and air, will be 

 studied. Perhaps other properties of radiating heat will be discov- 

 ered, or causes which modify the temperatures of the globe. But 

 all the principal laws of the motion of heat are known. This the- 

 ory, which rests upon immutable foundations, constitutes a new 

 branch of mathematical science. It is composed, at present, of differ- 

 ential equations of the motion of heat in solids and liquids, and of the 

 integrals of these first equations, and theorems relative to the equi- 

 librium of radiating heat. 



