NOTES. 475 



the gas evolved in fermentation, and that he found it to be 

 so by the very experiment now in use to show it, namely, 

 emptying half of a phial filled with lime water in the air of 

 a brewer's vat, when the remaining lime water becomes tur- 

 bid, the carbonate of lime being formed and precipitated ; 

 that he discovered on the same day the identity of fixed air 

 with that evolved from burning charcoal ; and finally, that 

 he also ascertained the air evolved from the lungs in re- 

 spiration to be fixed air, by breathing through a syphon 

 half filled with lime water. All this, which M. Cuvier 

 ascribes to Mr. Cavendish's discoveries, in 1766, had been 

 published by Dr. Black in 1755, and explained by the ex- 

 periments themselves being performed by his own hands, in 

 his public lectures, every year before nearly three hundred 

 persons, from the year 1757 to the time of Mr. Cavendish's 

 supposed discovery in 1766. Of these Lectures numberless 

 copies were taken, were in general circulation, and were sold 

 to the students attending the classes of the College in Edin- 

 burgh. It is, however, very possible that Mr. Cavendish 

 was not apprised of Dr. Black's experiment made before 

 1752 and published in 1755. But it is quite certain that 

 he never arrogated to himself the discovery of fixed air being 

 a peculiar body different from common air, for he expressly 

 says, " By fixed air I mean that peculiar species of factitious 

 air which is separated from alkaline substances by solution 

 in acids, or by calcination, and to which Dr. Black has given 

 that name in his Treatise on Quicklime." (' Phil. Trans.,' 

 LVL, p. 140.) Now this shows clearly that M. Cuvier never 

 had read Mr. Cavendish's paper, any more than he had read 

 Dr. Black's Treatise, and his Lectures. Another proof is his 

 asserting that Mr. Cavendish discovered the air evolved 

 from burning charcoal to be fixed air. His paper contains 

 not one word on that air as connected with burning char- 

 coal. Nay, so far is Mr. Cavendish from assuming to him- 

 self the discovery of its identity with the air evolved in fer- 

 mentation, that he expressly says Dr. Macbride had dis- 

 covered the evolving of fixed air in that process, and that he 

 himself only made his experiments to ascertain if any other 

 air was also evolved, when he found inflammable air also to 

 come away. Apparently he had not been aware of Dr. 

 Black's experiments in 1757. The Lectures would also 



