764 REPORT—1890. 
It is now necessary to examine Lavoisier’s claims rather more closely and in 
the light of M. Berthelot’s book. A réswmé of his work ‘On the Calcination of 
Tin’ was given by Lavoisier to the Academy in November 1774, but the complete 
memoir was not deposited until May 1777. A careful comparison of an abstract 
of what was stated to the Academy in November 1774, contributed by Lavoisier 
himself, in December 1774, to the ‘Journal de Physique’ of the Abbé Rozier, 
makes it evident that very substantial additions were made to the communication 
before it was finally printed in the ‘Mémoires de l’Académie des Sciences.’ The 
possibility of this is allowed by M. Berthelot. He says (p. 58): ‘A summary 
communication, often given wvd voce to a learned society, such as the Academy of 
Sciences of Paris or the Royal Society of London, would immediately call forth 
verifications, ideas, and new experiments, which would develop the range and even 
the results of such communication. The original author, when printing his 
memoir, would in return—and for this he is hardly blamable—embody these 
additional results and later interpretations. It thus becomes most difficult to 
assign wupertially to each his share in a rapid succession of discoveries.’ (Loc. 
cit. p. 58.) 
But although, as we shall see, Lavoisier was certainly aware of Priestley’s great 
discovery, no allusion is made to the gas, nor to Priestley’s previous work on the 
other constituent of air, which is printed in the ‘Philosophical Transactions’ for 
1772, and for which he was awarded the Copley Medal by the Royal Society. It 
is simply impossible to believe that Lavoisier could have been uninfluenced by this 
work, Indeed, we venture to assert that the full and clear recognition of the non- 
elementary nature of air which he eventually made was based upon it. It is 
noteworthy that in the early part of his memoir he states his opinion that the 
addition not only of powdered charcoal, but of any phlogistic substance, to a 
metallic calx is attended with the formation of fixed air. It is certain that at this 
period he had not only not consciously obtained any gas resembling Priestley’s 
dephlogisticated air from any calx with which he had experimented, but that none 
of his experiments had afforded him any idea that the gas absorbed during 
calcination was identical with it. 
At Easter 1775 Lavoisier presented a memoir to the Academy ‘On the 
Nature of the Principle which combines with Metals during Calcination.’ This 
was ‘relu de 8 aoiit, 1778.’ To the memoir there is a note stating that the first 
experiments detailed in it were performed more than a year before; those on the 
red precipitate were made by means of «a burning glass in the month of November 
1774, and were repeated in the spring of 1775 at Montigny in conjunction with 
M. Trudaine. In this paper Lavoisier first distinctly announces that the principle 
which unites with metals during their calcination, which increases their weight, 
and which transforms them into calces, is nothing else ‘than the purest and most 
salubrious part of the air; so that if that air which has been fixed in a metallic 
combination again becomes free, it reappears in a condition in which it is eminently 
respirable, and better adapted than the air of the atmosphere to support inflamma- 
tion and the combustion of substances,’ (‘(Huvres de Lavoisier,’ official edition, 
vol. ii, p. 123.) He then describes the method of preparing oxygen by heating the 
red oxide of mercury, and compares its properties with those of fixed air. There 
is, however, no mention of Priestley, nor any reference to his experiments. It can 
hardly be doubted that in this memoir Lavoisier intended his readers to believe 
that he was ‘the true and first discoverer’ of the gas which he afterwards named 
oxygen. This is borne out by certain passages in his subsequent memoir ‘On the 
Existence of Air in Nitrous Acid; Zu de 20 avril, 1776, vemis en décembre 1777. 
He had occasion incidentally to prepare the red oxide of mercury by calcining the 
nitrate, and says that he obtained from it a large quantity of an air ‘much purer 
than common air, in which candles burnt with a much larger, broader, and more 
brilliant flame, and which in no one of its properties differed from that which I 
had obtained from the calx of mercury, known as mercurius precipitatus per se, and 
which Mr. Priestley had procured from a great number of substances by treating 
them with nitric acid,’ | 
In another part of this memoir he says that ‘ perhaps, strictly speaking, there is _ 
