and of the Planetary Spaces. 63 
we call to mind the almost infinite velocity of radiation, that _ 
time enough has elapsed for the different layers of the earth, in 
passing to a solid state, to have lost all the heat developed during 
their change, and which escaped, by radiation, through the supe- 
_riour layers, still in a state of vapour; so that long prior to the 
present period, the last trace of this heat, however great it may 
have been, had disappeared. An effect similar to that we are 
now considering would result, for example, if we produce a hori- 
zontal cylinder, of great length, closed at the ends, and filled 
with steam at the temperature of the exteriour, and at the mazi- 
mum of density. In this position of the cylinder, the weight of 
the fluid would exercise no influence, and the pressure would be 
the same throughout the mass; but if we place this cylinder in a 
vertical position, the weight of the various layers of the fluid 
would produce a pressure, increasing in the direction of gravity, 
that of each being added to the preceding; and in this manner 
the several layers would become condensed to a liquid, in regu- 
lar succession. ‘The movement of each layer, during its descent, 
it would be difficult to determine, but, the time of its duration 
would certainly be sufficient for the latent heat of the liquefied 
vapour to escape, by radiation, if we suppose the sides of the cyl- 
inder, or even only its top to oppose no obstacle to radiation, or 
to be permeable to radiant heat; and in this manner the water 
of which the vapour had been composed would not become 
heated, but would preserve the temperature of the exteriour. 
In discarding, then, the opinion that the observed increase of 
temperature of the earth, with the increase of depth from its 
surface, is attributable to the original heat our globe may have 
had, I have proposed another explanation of this phenomenon, 
founded upon a cause of which the existence is certain, and 
which may certainly produce an effect similar to that which we 
observe. This cause is the inequality of heat in the regions of 
space traversed by the earth, in its movement therein, with the 
sun and all the planetary system. (6) The temperature of any giv- 
en point of space, or that which would be a by a thermo- 
meter placed at that point, is he radiant heat from 
the stars, which traverses space in all possible Zesetions. These 
stars form, around each point of space, an immense circumfer- 
(6) Has such a movement been recognized ¢ 
