6 Temperature of the Terrestrial Globe. 
» Thus the solar heat has accumulated in the interior of the globe 
and is there continually renewed. It penetrates the parts of the 
surface near the equator, and is dissipated through the polar regions. 
The first question of this kind which has been submitted to the cal- 
culus, is found in a memoir which I read to the French Institute, at 
the close of the year 1807, Art. 115, page 167. This article is 
deposited in the archives. I then took up this first question to ex- 
hibit a remarkable example of the application of the new theory ex- 
in the memoir; and to show how the analysis points out the 
tract followed by the solar heat in the interior of the earth. 
If now we replace this exterior envelop of the earth, whose points 
are not sufficiently deep to have a fixed temperature, we remark an 
order of facts more compound, the complete expression of which is 
given by our analysis. At a moderate depth, as three or four me- 
ters, the temperature observed does not vary during each day, but 
the change is very perceptible in the course of a year; it varies and 
and falls alternately. ‘The extent of these variations, that is, the 
difference between the maximum and minimum of temperature, is 
not the same at all depths; it is inversely as the distance from the 
surface. The different points of the same vertical line do not arrive 
at the same time at the extreme temperatures. The extent of the 
variations, the times of the year, which correspond to the greatest, 
to the mean, or to the least temperatures, change with the position 
of the point in the vertical line. There are the same quantities of 
heat which fall and rise alternately ; all these values have a fixed 
relation between themselves, which are indicated by experiments 
and expressed distinctly by the analysis. ‘The results observed are 
in accordance with those furnished by the theory ; no phenomenon 
is more completely explained. The mean annual temperature of 
of any point whatever in the vertical line, that is, the mean value of 
all those which might be observed in the course of a year, at this 
point, is independent of the depth. It is the same for all points of 
the vertical, and consequently that which would be observed imme- 
below the surface; it is the fixed temperature which exists 
at great depths. 
It is evident that in the enunciation of this proposition, we make 
no. account of the internal heat of the globe, and those accessory 
causes which would modify this result in a particular place. 
to ascertain general phenomena. We have be- 
fore remarked that the different effects can be separatel y considered. 
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