General Reflections on Heat. 79 
LECTURE, &c. 
GENTLEMEN, 
I have several times asserted, that Heat is the most im- 
poriant 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. ‘[o 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. 
a us then takea 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. Fainiliarity with the process of Compustion, has 
brought us to behold it under its ordinary forms without emo- 
tion: Isay 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, | 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 is no 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 
‘or 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 to a supposed principle 
