Temperature of the Terrestrial Globe. 17 
Although the effect of internal heat may be no longer sensible at 
the surface, the sum total of this heat which escapes in a given time, 
as in a year or a century, is measurable, and has been ascertained. 
That which escapes ina century through a square metre, and is dis- 
sipated in the celestial space, would melt a column of ice, of which 
the base should be a square metre, and height three metres. 
This result is derived from a fundamental proposition, which can 
be applied to all questions relating to the motions of heat, and espe- 
cially to that of terrestrial temperature. I allude to the differential 
equation, which expresses for each moment the state of surface. 
This equation, the truth of which is plain, and easily demonstrated, 
establishes a simple relation between the temperature of an element 
of the surface and the normal motion of heat. What renders this 
result of theory very important, and more valuable than any other 
for throwing light upon the questions which form the subject of this 
article, is, that it exists independent of the form and dimensions of 
bodies, and of the nature of the substances, whether homogeneous 
or not, of which the internal mass may be composed. The results 
of this equation are absolute: they are the same, whatever may have 
been the material constitution or original state of the glo 
We have published in the “Annales de Chimie et de Physique,” 
the abstract of a memoir, which has not yet been printed, and the 
object of which is to apply to the terrestrial globe the analyses of 
the motions of heat in a sphere or plane solid, of great dimensions. 
In that extract the principal formulas were exhibited, particularly 
those which express the variable state of a solid uniformly heated at 
a determinate and very great depth, or in its whole depth. If the 
original temperature, instead of being the same to a very great depth, 
results from successive immersions in several media, the 
ces are not less simple or remarkable. But this case, and several 
others which we have considered, are comprised in the general ex- 
pressions which have been mentioned. 
After having explained separately the principles of the inquiry 
respecting the temperature of the earth, in order to form a correct 
idea of these phenomena united, we ought to give, in a general 
statement, all the effects we bave just described. 
The earth receives the rays of the sun, which penetrate its mass, 
and are converted into non-luminous heat: it likewise possesses an 
internal heat with which it was created, and which is continually 
dissipated at the surface: and lastly, the earth receives rays of light 
Vor. XXXIL.—No. 1. 3 
