and the Mode of its Communication. 161 
liquid produced in that process ; and that the same quantity of 
heat reappears, when this liquid is congealed, and becomes a 
solid body. 
But, before I proceed any farther in these abstruse specula- 
tions, I shall endeavour to investigate some of the consequences 
W'hich would necessarily result from the radiations of hot and of 
cold bodies, supposing those radiations to exist, and their motions 
and actions to be regulated by certain assumed laws. 
And first, it is evident that the intensity of the rays emitted 
by a luminous point, in a perfectly transparent medium, is 
every where as the squares of the distance from that point, 
inversely ; for the intensity of those rays must be as their con- 
densation ; and their condensation being diminished, in propor- 
tion as the space they occupy is increased, if we suppose all the 
rays which proceed in all directions from any point, to set out at 
the same instant, and to move with the same velocity, in right 
lines, these simultaneous rays (or undulations) will, in their 
progress, form a sphere, which sphere will increase continually 
in size, as the rays advance ; and, as all the rays must be found 
at the surface of this sphere, their intensity, or condensation, 
must necessarily be as the surface of the sphere, inversely, or 
as the squares of the distance, inversely, from the centre of the 
sphere, or, which is the same thing, from the luminous point 
from which these rays proceed; the surfaces of spheres being to 
each other as the squares of their radii. 
Supposing now 7 , (what indeed appears to be incontrovertible, ) 
that the intensity of the rays which hot and cold bodies emit, in 
a medium perfectly transparent, follows the same law, we can 
determine what effects must be produced, by the largeness, or 
mdccciv. Y 
