THE ni Ami ACE b TIC AL JOURNAL AND TRANSACTION S 
[J une 3, 1871 
078 
much as the weights of the products furnished by the 
"burning of different combustibles are made up of the 
weights of the combustible burnt and of the oxygen 
consumed in the burning, these products are compound 
bodies—oxides, in fact, of the substances burnt. That 
inasmuch as given weights of many combustibles, as of 
hydrogen, sulphur, phosphorus, carbon and the metals, 
are not apparently made up of the weights of two or 
more distinct kinds of matter, these particular combusti¬ 
bles arc in effect elementary; as for the same reason is 
the oxygen with which, in the act of burning, they enter 
into combination. And lastly, that combustion or burn¬ 
ing consists in nothing else than in the union of com¬ 
bustible matter, simple or compound, with the empyreal 
matter, oxygen—the act of union being somehow attended 
by an evolution of light and heat. And except that it 
would be necessary nowadays to explain how, in certain 
eases of combustion, the combustible enters into union, 
not with oxygen, but with some analogue of oxygen, 
the above precise statement might equally well have 
been made by Lavoisier in 1785 or be made by one of 
ourselves at the present day. 
Lavoisier’s theory of combustion being known as the 
antiphlogistic theory, the question arises, What was the 
phlogistic theory to which it was opposed and which it 
succeeded so completely in displacing ? This phlogistic 
theory was founded and elaborated at the close of the 
seventeenth century by two German physicians, Beecher 
and Stahl. Having exercised a scarcely disputed au¬ 
thority over men’s minds until the notorious defection 
in 1785, it preserved for some years longer a resolute 
though tortuous existence, and was to the last defended 
;tnd approved by our own Priestley and Cavendish, who 
died, the former in 1801 and the latter in 1810. 
The importance attached to the refutation of this 
theory may be judged of from the circumstance that 
after the early experiments of Lavoisier on the composi¬ 
tion and decomposition of water had been successfully 
repeated by a committee of the French Academy in 
1790, a congratulatory meeting was held in Paris, at 
which Madame Lavoisier, attired as a priestess, burned 
on an altar Stahl’s celebrated ‘ Fundamenta Chemise 
Dogmatics ct Experimentalist solemn music playing a 
requiem the while. And the sort of estimation in which 
the Stahlian doctrines have since been held by chemists 
is fairly illustrated by a criticism of Sir J. Herschel, 
who, speaking of the phlogistic theory of chemistry, 
says that it “ impeded the progress of the science, as far 
as a science of experiment can be impeded by a false 
theory, .... by involving the subject in a mist of vi¬ 
sionary and hypothetical causes in place of the true 
acting principles.” Possibly, however, this much-abused 
theory may yet prove to contain an element of perma¬ 
nent vitality and truth ; anyhow the study of this earliest 
and most enduring of chemical theories can never be 
wholly devoid of interest to chemists. 
To appreciate the merit of the phlogistic theory it is 
necessary to bear in mind the period of its announce¬ 
ment. Its originator, Beecher, was bom in 1625, and 
died a middle-aged but worn-out man in 1682, a few 
years before the publication of the ‘ Principia.’ His more 
fortunate disciple, Stahl, who was born in 1660 and died 
in 1734, in his seventy-fifth }’ear, though afforded a possi¬ 
bility of knowing, seems equally with Beecher to have 
remained throughout his long career indifferent to the 
Newtonian principle that the weight of a body is pro¬ 
portionate to its quantity of matter,—that loss of weight 
implies of necessity abstraction of matter, and increase 
-of weight addition of matter. Whether or not the 
founders of the phlogistic theory conceived that change 
of matter in the way of kind, might equally with its 
•change in point of quantity, be associated with an alte¬ 
ra! ion in weight—and it must not be forgotten what 
pains Newton thought it necessary to take in order 
to show the contrary—certain it is they attached very 
little importance to the changes of weight manifested 
by bodies undergoing the metamorphoses of combus¬ 
tion. It might be that when combustible charcoal 
was burned the weight cf incombustible residue was 
less than the original weight of charcoal,—it might be 
that when combustible lead w r as burned the weight of 
incombustible residue was greater fhan the original 
weight of metal; this was far too trifling an unlikeness 
to stand in the way of the paramount likeness presented 
by the two bodies. For the lead and charcoal had the 
common property of manifesting the wonderful energy 
of fire ; they could alike suffer a loss of light and heat— 
that is, of phlogiston—by the deprivation of which they 
were alike changed into greater or less weights of inert 
incombustible residue. 
And not only were these primitive students of the 
philosophy of combustion unconscious of the fact and 
meaning of the relationship in weight subsisting between 
the consuming and the consumed body, but they were 
altogether ignorant of the part played by the air in the 
phenomena which they so boldly and successfully at¬ 
tempted to explain. Torricelli's invention of the baro¬ 
meter and Guericke’s invention of the air-pump were 
both indeed made during Beecher’s early boyhood: but 
years had to elapse before the consequent idea of the 
materiality of air could be domiciled, as it were, in 
human understandings. And not until more than a 
century after Torricelli’s discovery of the weight of air, 
—not, indeed, until the time of the great pneumatic 
chemists Black and Cavendish, and Priestley and 
Schcele, was it ever imagined that the aerial state, like 
the solid or liquid state, was a state common to many 
distinct kinds of matter; and that the weight or sub¬ 
stance of a rigid solid might be largely conti’ibuted to 
by the weight or substance of some constituent having 
its independent existence in the aerial or gaseous form. 
The notion that 100 lbs. of smithy-scales might consist of 
73 lbs. of iron and 27 lbs. of a particular kind of air, and 
that 100 lbs. of marble might consist of 56 lbs. of lime 
and 44 lbs. of another kind of air, was a notion utterly 
foreign to the older philosophy. Air, it was allowed, 
might be rendered mephitic by one kind of contamina¬ 
tion and sulphurous by another, and inflammable by a 
third; it might even be absorbed in, and so add to the 
weight of a porous solid, as water is absorbable by sand; 
but still air was ever indisputably air, essentially alike 
and unalterable in its mechanical and chemical oneness. 
This familiar conception had to be overcome, and the 
utterly strange notion of the largely aerial constitution 
of solid matter to be established in its stead, by the 
early pneumatic chemists, Black and Cavendish and 
Bergmann, before the deficiencies rather than positive 
errors of the phlogistic theory could be perceived. 
But long ere the foundation of modern chemistry had 
thus been laid, in 1756, by Black’s discovery of fixed 
air or carbonic acid as a constituent of mild alkalis and 
limestone, those old German doctors, Beecher and Stahl, 
though ignorant of the nature of air and neglectful of 
the import of gravity, had yet found something to say 
about the chemistry of combustion worthy of being de¬ 
fended a century afterwards by men like Priestley and 
Cavendish,—worthy, it is believed, of being recognized 
nearly two centuries afterwards as the expression of a 
fundamental doctrine in chemical and cosmical philo¬ 
sophy. They pointed out, for example, that the dif¬ 
ferent and seemingly unlike processes of burning, 
smouldering, calcining, rusting, and decaying, by which 
combustible is changed into incombustible matter, have 
a community of character ; that combustible bodies pos¬ 
sess in common a power or energy capable of being 
elicited and used, whereas incombustible bodies are devoid 
of any such energy or power; and lastly, that the 
energy pertaining to combustible bodies is the same in 
all of them, and capable of being transferred from the 
combustible body which has it to an incombustible body 
which has it not, rendering the body that was energetic 
and combustible inert and incombustible, and the body 
