8 Temperature of the Terrestrial Globe. 
trates the earth and returns into the air. Considering, therefore, a 
‘law similar to this, which is established of itself in the interior of the 
globe, I have obtained the following results. 
In one eighth of a year after the temperature at the surface is 
raised to its mean value, the earth begins to be heated; the rays of 
the sun penetrate it during six months. Then the heat of the earth 
takes an opposite direction ; it comes out and is dissipated in the air 
and external space. Now the quantity of heat which undergoes 
these variations in the course of a year is expressed by the calculus. — 
If the crust of the earth was formed of a metallic substance of forged 
iron, (the substance which I have chosen for an example, after hae 
ing measured the specific coeflicients,) the heat which produces 
the succession of the seasons, would be for the climate of Paris, and 
for a square meter of surface, equivalent to what would melt a cylin- 
drical column of ice, having for its base this square meter, and a 
height of about three meters and one tenth. Although. the value 
the coefficients for substances of which the globe is composed, 
has not as yet been measured, we can easily see that they would 
give a result much less than we have just mentioned. It is propor- 
tioned to the square root of the product of the capacity for heat, 
considered in relation to volume and the permeability. 
We will now consider the second cause of terrestrial heat, which, 
as we think, resides in the planetary spaces. The temperature of 
this space exactly defined, is that which a thermometer would indi- 
cate, supposing the instrument placed in any part of the space occu- 
pied by the solar system, and the bodies which compose this system 
annihilated. 
We shall give a detail of the principal facts from which we have 
ascertained the existence of this heat, peculiar to the planetary 
spaces, which is independent of the presence of the sun, and of the 
original heat which the earth has preserved. To obtain a knowledge 
of this singular phenomenon, it is necessary to ascertain what would 
be the thermometrical state of the terrestrial mass, if it received only 
‘the heat from the sun. To facilitate this enquiry we may at first 
— the atmosphere out of the account. Now if there existed no 
cause sufficient to give the planetary spaces a common and constant 
perature, that is, if the earth and all the bodies of the solar sys- 
tem, | = € placed i in space deprived of all heat, the phenomena ob- 
served would be altogether contrary to what we now witness. The 
would be subject to an intense cold and the decrease 
