[ lod J 
XXL. Letter from Rovert Hare, M.D. Professor of Chemi- 
stry in the University of Pennsylvania, &8c. &$c. to the Editor 
of the American Journal of Science and Arts, in Opposition | 
to the Conjecture that Heat may be Motion, and in favour of 
the Existence of a material Cause of calorific Repulsion*. 
Deak Sir,—Ln two memoirs published in your Journal, I have 
endeavoured to show that caloric and electricity are collateral 
agents in galvanism, the ratio of the former to the latter, in 
quantity, being as the extent of the operating superficies to the 
number of pairs into which it may be divided. In those publi- 
cations, I assumed that the causes of heat and electricity are 
material fluids. Although this view of the origin of calorific re- 
pulsion is taken by a great majority of chemists, it has been com- 
bated, both by Rumford and Davy: the former famous for his 
ingenious, instructive and laborious experiments ; and the latter 
distinguished by the most splendid discoveries. With the utmost 
deference for the authority of these great men, especially the lat- 
ter, I send the following remarks made in answer to his hypo- 
thetical views, which I shall here quote from his Elements in order 
to introduce the subject more intelligibly. 
“It seems possible,” says the illustrious author, ‘ to account - 
for all the phzenomena of heat, if it be supposed, 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 conceived 
greatest in the last, the particles have a motion round their own 
axes, with different velocities, the particles of elastic fluids mov- 
ing with the greatest quickness ; and that in ethereal substances, 
the particles move round their own axes, and, separating from 
each other, penetrate in right lines through space. ‘Tempera- 
ture may be conceived to depend upon the velocities of the vi- 
brations; 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 revo- 
lution of particles round their axes, at the moment when the 
body becomes liquid or aériform ; or from the loss of rapidity of 
vibration, in consequence of the motion of the particles through 
greater space. 
‘If a specific fluid of heat be admitted, it must be supposed 
liable to most of the affections which the particles of common 
matter are assumed to possess, to account for the phenomena ; 
* From Silliman’s Journal, No, IX. 
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