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the Source of the Heat excited by Friction. 
them, in order to examine them, if any should appear, I could 
perceive none; nor was there any sign of decomposition of 
any kind whatever, or other chemical process, going on in 
the water. 
Is it possible that the heat could have been supplied by means 
of the iron bar to the end of which the blunt steel borer was 
fixed ? or by the small neck of gun-metal by which the hollow 
cylinder was united to the cannon ? These suppositions appear 
more improbable even than either of those before mentioned; 
for heat Was continually going off, or out of the machinery , by 
both these passages, during the whole time the experiment 
lasted. 
And, in reasoning on this subject, we must not forget to 
consider that most remarkable circumstance, that the source 
of the heat generated by friction, in these experiments, ap- 
peared evidently to be inexhaustible. 
It is hardly necessary to add, that any thing which any in- 
sulated body, or system of bodies, can continue to furnish with- 
out limitation , cannot possibly be a material substance : and it 
appears to me to be extremely difficult, if not quite impossible, 
to form any distinct idea of any thing, capable of being excited, 
and communicated, in the manner the heat was excited and 
communicated in these experiments, except it be motion. 
I am very far from pretending to know how, or by what 
means, or mechanical contrivance, that particular kind of mo- 
tion in bodies, which has been supposed to constitute heat, is 
excited, continued, and propagated, and I shall not presume 
to trouble the Society with mere conjectures ; particularly on 
a subject which, during so many thousand years, the most 
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