éreneral Reflections on Heat. 7 
LECTURE, &x. 
GENTLEMEN, 
I have several times asserted, that Heat is the most im- 
portant agent in the Natural World,—at least of all those 
agents that come under the cognizance of the chemist. Its - 
influence over matter is surprisingly extensive; its effects 
are exceedingly diversified. ‘To the phenomena of Heat 
your attention was called at.an early period of our course ; 
but it isonly at anadvanced siage of chemical studies, that one 
is qualified to appreciate the full importance of this agent. 
Let us then take a general review of the effects of heat, as 
they are exhibited in combustion and natural temperature ; 
as the great source of power in the physical world; as con- 
trolling chemical phenomena ; and as allied with the princi- 
ple of life itself. 
1. Familiarity with the process of Comsusrion, has 
brought us to behold it under its ordinary forms without emo- — 
tion: I say under its ordinary forms; for when it is present- - 
ed to us under any unusual shape, we still contemplate it 
with delight and admiration. Among the numerous and di- 
versified experiments, that accompany a course of chemical 
lectures, I have never found any class appear to interest the 
spectators so much, as those attended by combustion, espe- 
cially when supported by oxygen gas. Indeed, the taper, 
which is the first object that arrests the infant eye ; the bon- 
fires, that raise such ecstasy in the days of childhood; the illu- 
minated city, that proclaims the joys of peace; conspire to 
testify how pleasing is this spectacle to the eye of man. 
Exhibited also, as it sometimes is, in the burning of a forest 
by night, or in the conflagration of a city, where can we find 
objects that comprise more elements of the true sublime ? 
It isno wonder therefore, that to account for the pheno- 
mena of combustion, has been an object of long and earnest 
inquiry. Indeed the attempt to explain it formed almost the 
first philosophical theory, that was ever instituted to account 
for a class of chemical phenomena; and various other at- 
tempts, more or less successful, have been made in later 
times. 
Combustion was at first accounted for by ascribing it to the 
agency of Phlogiston, a name given toa supposed principle 
