relative to Black, Watt, and Cavendish. 521 



ter acquainted with sciences not peculiarly his own : but 

 though the subject is chemistry, though you have attended 

 Black's lectures, and though Black's own discoveries are in 

 question, I greatly fear that on almost every point in which 

 you differ from Cuvier you are yourself in the wrong. 



Thus, you are certainly wrong in denying Cuvier's asser- 

 tion — that permanently elastic fluids were measured by Hales; 

 and you have only to consult the * Analysis of the Air,' to be 

 convinced of your mistake. 



Again, you are wrong in denying Cuvier's assertion, that 

 " no one before Cavendish had distinguished fixed air as a 

 separate aeriform substance:" and you need only look at 

 Black's treatise to assure yourself that he declined to decide, 

 for want of evidence, whether it was an aeriform substance, 

 or not; and left it among the class of — "bodies of which it is 

 difficult to say, whether they are really combined with the 

 aerial particles, or are merely suspended in the fluid, in con- 

 sequence of their being of the same specific gravity*." 



But above all, you are most wrong in reprehending the for- 

 mer Secretary of the Institute, for " making no mention what- 

 ever of Watt in connection with the discovery of the composition 

 of water " — for not confounding, that is, the rights of disco- 

 very — for not falsifying the history of chemistry in one of its 

 most material parts — for not representing Watt as the claim- 

 ant of a merit to which he had not the smallest pretensions — 

 and thus degrading, with intent to exalt, the venerable name 

 of one who has entitled himself to the admiring gratitude of 

 ages, by realising, beyond any other man, the vision which 

 Bacon saw — of experimental works of fruit. 



You have no sufficient ground, I think, for imputing to — 

 " a person of M. Cuvier's eminent attainments, filling the high 

 office of * Secretaire perpetuelf and charged with the delicate 

 and important duty of recording the history of science yearly" 

 — that "he has not read Mr. Cavendish's paper f» or Dr. 



* Cavallo on Air, p. 361. 1781. Hawksbee approached the nearest to 

 the discovery of the different density of gases, as early as 1707; — "whether," 

 said he, "the space deserted by the water [after an explosion of gunpowder 

 in a close vessel] is possessed by a body of the same weight and density, or is 

 of the same quality, as common air, I dare not determine; since an experi- 

 ment I have lately made seems to conclude it otherwise." He observed like- 

 wise " a loss, or absorption of this air, after it had reached its former tem- 

 perature;" and suggested that a temporary distension of the springs or 

 constituent parts, of the ambient air, as well as of those contained in the 

 body of the gunpowder, may account for " this odd phcenomenon." — Phil. 

 Trans, vol. xxv. p. 2409. 



t One of Lord Brougham's reasons for thinking that Cuvier had never 

 read Cavendish's paper is, that he says, — " Cavendish unfolded his disco- 

 veries in a manner even more striking than the discoveries themselves''— 



Phil. Mag. S. 3. No. 190. Suppl. Vol. 28. 2 N 



