762 REPORT— 1890. 
tary of the French Academy, has recently published, under the title of ‘ La Révo- 
lution Chimique,’ a remarkable book, written with great skill, and with all the 
charm of style and perspicacity which invariably characterise his work, in which 
he claims for Lavoisier a participation in discoveries which we count among the 
chief scientific glories of this country. From the eminence of M. Berthelot’s posi- 
tion in the world of science his book is certain to receive in his own country the 
attention which it merits, and as it is issued as one of the volumes of the Biblio- 
théque Scientifique Internationale it will probably obtain through the medium of 
translations a still wider circulation. I trust that I shall not be accused of being 
unduly actuated by what Mr. Herbert Spencer terms ‘the bias of patriotism’ in 
deeming the present a fitting occasion on which to bring these claims to your notice 
with a view of determining how far they can be substantiated. 
All who are in the least degree familiar with the history of chemical science 
during the last hundred years will recognise, as I proceed, that the claims which 
M. Berthelot asserts on behalf of his illustrious predecessor are not put forward for 
the first time. Explicitly made, in fact, by Lavoisier himself, they were uni- 
formly and consistently disallowed by his contemporaries. M. Berthelot now 
seeks to support them by additional evidence and to strengthen them with new . 
arguments, and asks us thereby to clear the memory of Lavoisier from certain grave 
charges which lie heavily on it. You have doubtless anticipated that these claims 
have reference to Lavoisier’s position in relation to the discovery of oxygen gas and 
the determination of the non-elementary nature of water. 
The substance we now call oxygen—a name we owe to Lavoisier—was discovered 
by Priestley on August 1, 1774; he obtained it, as every schoolboy knows, by the 
action of heat upon the red oxide of mercury. We all remember the character- 
istically ingenuous account which Priestley gives of the origin of his discovery. 
M. Berthelot sees in it merely the evidence of the essentially empirical character 
of his work. ‘ Priestley,’ he says, ‘the enemy of all theory and of every hypothesis, 
draws no general conclusion from his beautiful discoveries, which he is pleased, 
moreover, not without affectation, to attribute to chance. He describes them in 
the current phraseology of the period with an admixture of peculiar and incoherent 
ideas, and he remained obstinately attached to the theory of phlogiston up to his 
death, which occurred in 1804’ (p. 40). Such a statement is calculated to give an 
erroneous idea of Priestley’s merit as a philosopher. That the implication it con- 
tains is wholly opposed to the real spirit of his work might be readily shown by 
numerous quotations from his writings, Perhaps this will suffice: ‘It is always 
our endeayour, after making experiments, to generalise the conclusions we draw 
from them, and by this means to form a theory or system of principles to which 
all the facts may be reduced, and by means of which we may be able to foretell the 
result of future experiments.’ This quotation is taken from the concluding chapter 
of his ‘Experiments and Observations on Different Kinds of Air,’ in which he 
actually seeks to draw ‘general conclusions’ concerning the constituent principles 
of the various gases which he himself made known to us and to show the bear- 
ing of these conclusions on the doctrine of phlogiston. That he was content to 
rest in the faith of Stahl’s great generalisation, even to the end, is true, and the 
fact is the more remarkable when we recall the absolute sincerity of the man, 
his extraordinary receptivity, and, as he says of himself, his proneness ‘to em- 
brace what is generally called the heterodox side of almost every question.’ If 
it is argued that this merely shows Priestley’s inability to appreciate theory, it 
must be at least admitted that there is no proof that he was inimical to it. His 
position is clearly evident from the concluding words of the section of his 
work from which I have already quoted: ‘This doctrine of the composition and 
decomposition of water has been made the basis of an entirely new system of 
chemistry, and a new set of terms has been invented and appropriated to it. It 
must be acknowledged that substances possessed of very different properties may, 
as I have said, be composed of the same elements in different proportions and 
different modes of combination. It cannot, therefore, be said to be absolutely zm- 
possible but that water may be composed of these two elements or any other. But 
then the supposition should not be admitted without proof; and if a former theory 
Se ee 
