1817] On the Chemical Phenomena of Heat. 428 
This hypothesis is founded upon an assumption which cannot be 
admitted fora moment ; that the particles of solids are in a constant 
state of vibratory motion, What proof have we of this? If this 
be the case, the atoms or corpuscules which constitute the hardest 
and densest solids cannot be in contact, except when they impinge 
upon each other; which contact can only continue for an indefi- 
nitely small portion of time; and solidity, I affirm, cannot exist 
except these atoms are really in mathematical contact. The reason 
is obvious: at equal distances from equal and similar corpuscules, the 
forees will be equal; if these be not in contact, they must have 
perfect freedom of motion round each other, which is the property 
only of fluids and elastic matter. Allowing this objection to be in- 
valid, upon what physical principles or law of nature can this mo- 
tion be produced; and when produced, how is it preserved from 
diminution? Such a motion is more than perpetual ; it has con- 
stantly to oppose an antagonist force, sometimes less than, at others 
equal to, and sometimes greater than itself. Upon no principle can 
it be shown that this motion can be preserved from diminution and 
final decay. It is certainly unphilosophical to assume the existence 
of such a motion, unless we can prove that it can be maintained 
under all circumstances. How do these principles explain the phe- 
nomena of the different capacities of bodies for heat, and of latent 
heat? It has certainly been affirmed that the immediate cause of 
the phenomena of heat is motion, and the laws of its communica- 
tion are precisely the same as the laws of the communication of 
motion. No one has ever, as far as I can learn, pointed out any 
similarity; nor has any analogy been proved to exist between the 
intensity of temperature and the velocity of vibration of indefinitely 
small atoms of ponderable matter; or between capacity for heat, 
and the extent of the vibratory motion. I shall make no observa- 
tions upon the convertability of this vibratory motion of a minute 
atom into revolution round an axis, excepting that it is impossible ; 
requesting those who maintain its possibility to explain upon what 
physical principles it can take place, and show the real difference in 
constitution which exists between solids and liquids; and that when- 
ever a body has arrived at a certain temperature, or, in other words, 
the vibrating motion has attained a certain velocity, the revolution 
round the axis must regularly take place; also, for which there is 
no provision, the difference between fluids and gases; the definite 
and constant temperature at which a liquid assumes the gaseous 
form, and the reason why this point of ebullition is less in vacuo 
than under atmospheric pressure. It is perhaps possible for all this 
to be correct; but it is repugnant to common sense; and, until it 
shall be established upon undeniable principles, must be inadmis- 
sible. What is stated concerning ethereal substances, or what are 
with greater propriety denominated ,imponderable agents, is cer- 
tainly correct in part. 'When these agents possess freedom of mo- 
tion, their particles, if they consist of particles, must separate from 
