TRANSACTIONS. 
71 
narrowed as new facts arise. This has happened to the theory 
of Lavoisier, in consequence of its having been discovered 
that combustion is not necessarily accompanied with an absorp¬ 
tion of oxygen, and that acids exist independently of oxygen, 
regarded by him as the general acidifying principle. But after 
all the deductions that can justly be made on that account 
from the merits of Lavoisier, he must still hold one of the 
highest places among those illustrious men, who have advanced 
chemistry to its present rank among the physical sciences. It 
is deeply to be lamented that his fame, otherwise unsullied, 
should have been stained by his want of candour and justice to 
Dr. Priestley, in appropriating to himself the discovery of 
oxygen gas. This charge, often preferred and never answered, 
would not have been revived in this place, but for the claim so 
recently and indiscreetly advanced by M. Victor Cousin. To 
the credit of Dr. Priestley it may be observed, that in asserting 
his own right, he exercised more forbearance than could reason¬ 
ably have been expected under such circumstances. In an un¬ 
published letter to a friend, he thus alludes to the subject of 
M. Lavoisier’s plagiarism. “He” (M* Lavoisier) “is an In¬ 
tend ant of the Finances , and has much public business, but 
finds leisure for various philosophical pursuits, for which he is 
exceedingly well qualified. He ought to have acknowledged 
that my giving him an account of the air I had got from mer - 
curius calcinatus, and buying a quantity of M. Cadet while I 
was at Paris, led him to try what air it yielded, which he did 
presently after I left. I have, however, barely hinted at this 
in my second volume The communication alluded to was 
made by Dr. Priestley to M. Lavoisier in October, 1774; 
and the Memoir, in which the latter assumes to himself the 
discovery that mercurius calcinatus (red oxide of mercury) 
affords oxygen gas when distilled per se , was not read to the 
Academy of Sciences before April, 1775f. In evincing so 
little irritability about his own claim, and leaving its vindication 
with calm and just confidence to posterity, the English philo¬ 
sopher has lost nothing of the honour of that discovery which 
is now awarded to him, by men of science of every country, 
as solely and undividedly his own. 
WEDNESDAY EVENING. 
Mr. R. Potter, Jun. read a description of his new construc¬ 
tion of Sir Isaac Newtons reflecting microscope , and exhibited 
* Letter to the late Mr. Henry, dated Caine, Dec. 31, 1775. 
f See an Abstract of this Memoir in the Journal dc Rozier, Mai, 1775. 
