Philosophical Character of Dr. Priestley. 39 



same period with Dr. Priestley, was following, in a distant part of Eu- 

 rope, a scarcely less illustrious career. * ' . 



It is the natural progress of most generalizations in science, that 

 at first too hasty and comprehensive, they require to be narrowed as 

 new facts arise. This has happened to the theory of Lavoisier, in 

 consequence of its having been discovered,, that combustion is not ne- 

 cessarily accompanied with an absorption of oxygen, and that acids 

 exist independently of oxygen, regarded by him as the general acidi- 

 fying 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 candor and justice to Dr. Priest- 

 ley, 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 reasonably have been expected under such 

 circumstances. In an unpublished letter to a friend, he thus alludes 

 to the subject of M. Lavoisier's plagiarism. " He," (M. Lavoisier) 

 "is an Intendant 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 acknowleged that my 

 giving him an account of the air I had got from Mercurius Calcin- 

 atus, 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. Lavois- ' 

 ier in October, 1774; and the Memoir, in which the latter assumes 

 to himself thfe -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, 1775.f In evincing so little 

 irritability about his own claim, and leaving its vindication with calm 

 and just confidence to posterity, the English philosopher has lost 

 nothing of the honor of that discovery, which is now awarded to 

 him, by men of science of every country, as solely and undividedly 

 his own. 



Letter 



— _ , j j , — 



t Sec an Abstract of this Memoir in the Journal de Rozier, Mai, 1775. 



