336 BLACK. 



combustion, and on oxidation, further than to say that 

 he had for a considerable time been engaged in these 

 inquiries. It was not indeed till 1 787 that he became 

 a convert to the sound and rational doctrine, and 

 abandoned the fanciful hypothesis, simple and inge- 

 nious though it be, of Stahl. Berthollet, the earliest 

 convert, had come over to the truth two years be- 

 fore. Thus, discoveries had been made which laid the 

 foundation of a new science, and on which the atten- 

 tion of all philosophers was bent ; yet the greatest 

 scientific work of the age made no more mention 

 of them than if Black, Cavendish, Priestley, and 

 Scheele had not been. The conjecture may be allowed 

 to us, that if any of these great things had been done 

 in France, M. Morveau would not have been suffered 

 to preserve the same unbroken silence respecting them, 

 even if his invincible prejudices in favour of the doc- 

 trine of phlogiston had disposed him to a course so 

 unworthy of a philosopher. 



The detail into which I have entered, sufficiently 

 proves that the discovery of fixed air laid at once the 

 foundation of the great events in the chemical world 

 to which reference has just been made, because the 

 step was of incalculable importance by which we are 

 led to the fact that atmospheric air is only one of a 

 class of permanently elastic fluids. When D'Alem- 

 bert wrote the article ' Air/ in 1751, he gave the doc- 

 trine then universally received, that all the other kinds 

 of air were only impure atmospheric air, and that this 

 fluid alone was permanently elastic, all other vapours 

 being only, like steam, temporarily aeriform. Once 

 the truth was made known that there are other gases 



