80) General Reflections on Heai- 
of inflammability, residing in combustible bodies. This ex- 
planation amounted to little more than to say, combustion is 
eaused by the principle of combustion. in the same manner 
we might account for the origin of light, by ascribing its phe- 
nomena to the td/uminating principle ; which is obviously ne 
explanation at all. There was no proof of the existence of 
sucha substance in inflammable bodies as Phlogiston was sup- 
posed to be, and there were certain phenomena, already fa- 
miliar to you, which were inconsistent with the supposition 
that bodies lose an ingredient in their composition during 
combustion. When a more rigorous mode of reasoning was 
introduced into our science, by those master spirits that laid 
its present foundations, the fallacy of this explanation was 
fully perceived; and the hypothesis would probably have 
been much sooner abandoned by its advocates, had not the 
discovery of hydrogen furnished them with a real substance, 
which they could substitute for the unmeaning phrase “ in- 
flammable principle.’? Aecording to the Phlogistic theory, 
thus modified, “‘ combustion is owing to the separation of 
hydrogen.” Almost all those combustibles which burn with 
flame, do in fact contain hydrogen ; and flame, it is true, is 
commonly nothing more than burning hydrogen, either alone 
or in combination with carbon. Still there are combustibles, 
as phosphorus and sulphur, which burn with flame, and yet 
contain no hydrogen,—faets which are quite suflicient to 
overthrow the hypothesis, that combustion is Owing to the 
separation ofhydrogen. Indeed, if it could be proved, that 
in all cases of combustion, hydrogen is separated, combustion 
itself would remain unaccounted for. This discovery would 
teach us what it ¢3 that is burning, but it would not tell us 
what makes it burn. What would they say of hydrogen itself ’ 
Does that burn by the extrication of hydrogen? It is evident 
that the burning of hydrogen, as well as that of every other 
combustible, is an effect, a consequent, dependent on some 
cause which had not at that time been discovered ; for if 
hydrogen were admitted to be the substance on fire in every 
case of combustion, the questions would still recur, what sets 
iton fire ? what keeps it on fire? 
The discovery of oxygen gas led the way to the first ra- 
tional views that ever were entertained respecting the cause 
ef combustion. It ascertained the immediate agent on 
which this procéss depends. But in order to render the ob-, 
servations which I propose to éffer on Lavoisier’s Theory of 
