10 Temperature of the Terrestrial Globe. 



regions. We cannot conceive of the existence of such a system of 

 luminous and heated bodies without admitting that any point of space 

 whatever which contains these bodies acquires a fixed temperature. 



The immense number of bodies compensates for the inequalities 

 in their temperatures, and renders radiation sensible and uniform. 



This temperature of space is not the same in different regions of 

 the universe ; but it does not vary in the regions in which are situa- 

 ted the planetary bodies ; because the dimensions of this space are 

 incomparably smaller than those distances which separate it from 

 the radiating bodies ; for example, in all points of the orbit of the 

 earth this planet finds the same temperature. 



It is the same with other planets of our system : they all equally 

 participate in the common temperature, which is more or less aug- 

 mented for each one of them, by the rays of the sun, according to 

 the distance of the planet from that body. Respecting the inquiry 

 what must be the temperature of each of the planets, the principles 

 which must settle it, furnished by an exact theory, are as follows. 

 The intensity and distribution of heat on the surface of these bodies 

 results from the distance of the sun, the inclination of the axes of 

 rotation to the orbit, and the state of the surface. It is very differ- 

 ent even in its mean value, from what would be indicated by a ther- 

 mometer insulated in the place of the planet, for the solid state, 

 the very great dimensions, and doubtless the presence of an atmos- 

 phere and the nature of the surface, determine the mean value. 



The original heat which has been preserved in the interior, has 

 long since ceased to have a very sensible effect upon the surface. 

 For the present state of the crust of the earth shows us that the 

 primitive heat of the surface is almost entirely dissipated. From 

 the constitution of the solar system it is very probable that the tem- 

 perature of the poles of each planet, or at least of the greatest part 

 of them, is little less than that of space. This polar temperature is 

 the same for all these bodies, although their distances from the sun 

 may be unequal. 



We can determine with some degree of precision, the temperature 

 which the earth would have acquired if situated in the place of each 

 of the planets; but the temperature of the planets themselves, can- 

 not be ascertained ; for in order to that we must know the state of 

 the surface and the atmosphere. However, this uncertainty no longer 

 exists as to the bodies which are placed at the extremities of the solar 

 system like the planet Uranus. The impression of the solar rays 



