422 On the Chemical Phenomena of Heat. [Jony, 
the other centrifugal; and when the temperature of any body is the 
same as that of the surrounding medium, these forces, acting be- 
tween any two adjacent particles, must balance each other. 
Of the nature of the centripetal foree we know but little; it is 
probably, as I shall subsequently show, a modification of that 
power which causes the great bodies of the planetary system to tend 
towards each other. As, however, an investigation of this subject 
is intimately connected with the chemical agencies of electricity, I 
shall not examine into the nature of this centripetal force till, ina 
future paper, the relations of heat to light and electricity have been 
considered. As we know of no centripetal force which deviates 
‘ : i 
from the general law, viz. force varying as qx. Ishallassume, 
in the present paper, this as the probable law of corpuscular action, 
by which I mean the action of one corpuscule upon another, and not 
that of a system of corpuscules uponone. From the circumstance 
of corpuscular action in solids vanishing at inconceivably small dis- 
tances, the force which preserves the aggregation of solids has been 
supposed to vary much more rapidly than = This apparent de- 
viation I shall subsequently prove arises from the mode of action 
arising from the order of arrangement of the corpuscles in solids. 
The centripetal force is the effect of that which produces the sen- 
sations of heat, and is usually denominated calorific repulsion. Two 
different hypotheses have been advanced to account for the effect of 
heat, so far as it is concerned in the phenomena of expansion, con- 
traction, and chemical decomposition. Of these, one appearing to 
me totally erroneous, and the other only defective, I shall examine 
into and state the arguments by which I have been induced to reject 
the one supported principally by Count Rumford, and choose that 
first proposed by Dr. Black and Lavoisier. 
The one supposes that in solids the particles are in a constant state 
of vibratory motion, the particles of the hottest bodies moving with 
the greatest velocity, and through the greatest space ; that in liquids 
and elastic fluids, besides the vibratory motion, which must be con- 
ceived greatest in the last, the particles have a motion round their own 
axis with different velocities, their particles of elastic fluids moving 
with the greatest quickness ; and that in etherial substances the par- 
ticles move round their own axes, and separate from each other, 
penetrating in right lines through space. Temperature may be 
conceived to depend upon the velocities of their vibrations ; increase 
of capacity on the motion being performed in greater space, and 
the diminution of temperature during the conversion of solids into 
fluids or gases, may be explained on the idea of the loss of vibratory 
motion in consequence of the revolution of particles round their 
axes, at the moment when the body becomes fluid or aeriform, or 
from the loss of rapidity of vibration in consequence of the motion 
of the particles through greater space. 
