NOTES. 509 



looked at the Lectures, he would have found that two years 

 after the publication of his capital discovery, viz., in 1757? 

 and one year before Mr. Cavendishes paper was received, 

 Dr. Black discovered that fixed air is the gas evolved in fer- 

 mentation, and that he found it to be so by the very experi- 

 ment 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 turbid, 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 respiration 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 experiments 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 ge- 

 neral circulation, and were sold to the students attending 

 the classes of the College in Edinburgh. 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 alcaline substances by 

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

 has given that name in his Treatise on Quicklime." ( f 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 

 charcoal. Nay, so far is Mr. Cavendish from assuming to 

 himself the discovery of its identity with the air evolved in 

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



