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 
airin 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. 
I 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 tothe 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 * Recuetls Sctentifiques,” 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. 
