LAVOISIER. 303 



light on the constitution of the atmosphere, which he 

 had not derived from his similar experiments in 1770, 

 and 1771, upon the reduction of minium, and the cal- 

 cination of other metals. But the discoveries of Dr. 

 Priestley must have been known to him in 1774; and 

 what he gives as his conjectures derived from his own 

 experiments, were the discoveries of Dr. Priestley in 

 1772 and 1774. The knowledge of these discoveries 

 formed the only difference between the state of M. 

 Lavoisier's information, when he experimented upon 

 tin in 1773 and 1774, and when he experimented on 

 lead three years before. It is perfectly clear that until 

 the discoveries of Dr. Priestley, the chief of which, 

 we have positive evidence, was communicated to him 

 by the Doctor himself, he never had the least idea of 

 the air absorbed in calcination possessing any qualities 

 like those of oxygen gas, or had supposed that the air 

 evolved in the reduction of calcined metals, was of that 

 nature ; indeed, he distinctly stated it to be fixed air, 

 misled by the quantity of fixed air found in minium as 

 an impurity. He had made many experiments on calces 

 of metals, and he had never found any air to be con- 

 tained in them resembling oxygen. Until he heard of 

 Dr. Priestley's great experiment he never had thought 

 of obtaining oxygen gas from those bodies, nor ever 

 knew of the existence of that gas. 



This is the plain inference from the history of his 

 inquiries, as far as we have now followed it. But as he 

 has himself, beside wrapping up the date of his theory 

 in the general terms already observed when he presented 

 his paper on tin, also laid positive claim to the disco- 

 very of oxygen in a subsequent Memoir, it becomes 

 necessary to examine the grounds of this pretension 

 more closely, and we shall find that this examination 

 entirely confirms the position already stated, namely, 

 his ignorance of oxygen, until the true discoverer made 

 him acquainted with it. 



We shall first give the words in which he couches 



