TRANSACTIONS OF SECTION B. 765 
nothing in it of which Mr. Priestley would not be able to claim the original idea; 
but as the same facts have conducted us to diametrically opposite results, I trust 
that, if I am reproached for having borrowed my proofs from the works of this 
celebrated philosopher, my right at least to the conclusions will not be contested.’ 
M. Berthelot remarks on the irony of this passage: we may infer from it 
that the friends of the English chemist had not been altogether idle. In his 
memoir ‘On the Respiration of Animals,’ read to the Academy in 1777, he again 
appears to admit the claim of Priestley to at least a share in the discovery: ‘It is 
known from Mr. Priestley’s and my experiments that mercurius precipitatus per se is 
nothing but a combination’ &c. In several subsequent communications Priestley’s 
name is mentioned in very much the same connection, until we come to the 
classical memoir ‘On the Nature of the Acids,’ when it is said: ‘I shall henceforth 
_ designate the dephlogisticated air, or the eminently respirable air... by the 
_ name of the acidifying principle, or, if it is preferred to have the same signification 
_ under a Greek word, by that of the “principe oxygine.”’ 
In none of the memoirs after that of Easter 1775 is the claim for participation 
more than implied ; it is made explicitly for the first time in the paper ‘On a 
Method of Increasing the Action of Fire,’ printed in the ‘ Mémoires de l’Académie’ 
for 1782, and in these words: ‘It will be remembered that at the meeting of 
Easter 1775 I announced the discovery, which I had made some months before 
with M. Trudaine, in the laboratory at Montigny, of a new kind of air, up to then 
absolutely unknown, and which we obtained by the reduction of mercurius pre- 
- eipitatus per se. This air, which Mr, Priestley discovered at very nearly the same 
time as I, and I believe even before me, and which he had procured mainly from 
the combination of minium and of several other substances with nitric acid, has been 
named by him dephlogisticated air.’ 
In the ‘Traité Elémentaire de Chimie’ the claim for participation is again asserted 
in these words: ‘This air, which Mr, Priestley, Mr. Scheele, and I discovered at 
about the same time... ’ 
Now there is no question that Lavoisier knew of the existence of oxygen some 
months before he made the experiments with the burning glass of M. Trudaine at 
Montigny for the simple reason that Priestley had already told him of it. Priestley 
left Leeds in 1773 to become the librarian and literary companion of Lord Shel- 
burne, and in the autumn of 1774 he accompanied his lordship on to the Continent, 
and spent the month of October in Paris. Lavoisier was famous for his hospitality; 
his dinners were celebrated ; and Priestley, in common with every foreign savant of 
note who visited Paris at that period, was a welcome guest. What followed is 
best told in Priestley’s own words: ‘Having made the discovery [of oxygen] some 
time before I was in Paris, in the year 1774, I mentioned it at the table of 
Mr. Lavoisier, when most of the philosophical people of the city were present, 
saying that it was a kind of air in which a candle burnt much better than in 
comm: air, but I had not then given it any name. At this all the company, and 
Mr. an i Mrs. Lavoisier as much as any, expressed great surprise. I told them I 
had gotten it from precipitate per se and also from red lead. Speaking French very 
imperfectly, and being little acquainted with the terms of chemistry, I said plombe 
rouge, which was not understood till Mr. Macquer said I must mean miniwm,’ 
In his account of his own work on dephlogisticated air, given in his ‘Observa- 
tions,’ &c., 1790 edition, he further says, vol. ii. p. 108: ‘Being at Paris in the 
October following [the August of 1774], and knowing that there were several 
very eminent chemists in that place, I did not omit the opportunity, by means of 
_ my friend Mr. Magellan,’ to get an ounce of mercurius caleinatus prepared by Mr. 
_ Cadet, of the genuineness of which there could not possibly be any suspicion: and, 
at the same time, I frequently mentioned my surprise at the kind of air which 
1M. Trudaine de Montigny died in 1777. 
? Prof. Grimaux (Lavoisier, p. 51), says: ‘Un de ses | Lavoisier’s] amis qui habitait 
_ Londres, Magalhaens ou Magellan, de la famille du célébre navigateur, lui envoyait 
tous les mémoires sur les sciences qui paraissaient en Angleterre et le tenait au 
courant des découvertes de Priestley.’ 
