relative to Black, Watt, and Cavendish. 523 



so often dazzled and delighted your hearers, something that 

 should have been kept back would occasionally slip out, of 

 which an astute adversary did not fail to make his advantage. 

 And even so it is still : from the Jlfteen critical pages you have 

 allowed one criticism to creep out, as too good to be sup- 

 pressed. And here it is : — 



*' I leave him" (the author of this heap of errors) "in the 

 hands of M. Arago, who will observe with some wonder that 

 he has been accused, and judged, and condemned, by a che- 

 mist so well-versed in that science, and so reflecting, as to 

 announce the astonishing novelty — that the exhibition of sul- 

 phur to sulphuric acid reduces that acid, and restores it to its 

 primitive state of sulphur ! The writer had probably read 

 somewhere that sulphuric acid is reduced to sulphurous by the 

 process ; for he is assuredly the first that had ever hit upon 

 the acid's reduction by sulphur to 'its primitive state'*." 



Now we will at least give credit to the present perpetual 

 Secretary of the Institute, to whose scorn you devote the un- 

 happy Reviewer, for having read the papers of Cavendish; 

 and he would no doubt recollect this remarkable passage in the 

 " experiments on factitious airs " (1 764-) to which the Reviewer 

 should seem to be referring — " Sulphur is allowed by che- 

 mists to consist of the plain vitriolic acid united to phlogiston; 

 the volatile sulphureous acid appears to consist of the same 

 acid united to a less proportion of phlogiston than what is re- 

 quired to form sulphur; a circumstance which I think shows 

 the truth of this is, that if oil of vitriol be distilled from sul- 

 phur, the liquor which comes ever will be the volatile sul- 

 phureous acid." M. Arago might perhaps compare these 

 early notions of Cavendish with the Reviewer's account of the 

 phlogistic opinions, not in your interpolated words, but in his 

 own — (i It was concluded therefore that it was the same phlo- 

 giston which was derived from all those substances (charcoal, 

 sugar, metallic bodies, ike), however different in their nature: 

 a similar succession of phenomena is presented by sulphur: 

 if it be burnt, it forms sulphuric acid; but if the acid thus 

 formed be heated with phosphorus, or charcoal, or sugar, or 

 even sulphur itself, it is equally restored to its primitive state f," 

 — and having read this account, supposing M. Arago for a 

 moment to be only as experienced, as learned, and as practical 

 a chemist, as he whom you have consulted out of court, and no 

 more — supposing him, that is, to believe, with your anonymous 

 friend and yourself, that the total reduction of sulphuric acid 

 by sulphur is a laughable absurdity — M. Arago would yet see, 



* Brougham's Lives, vol. ii. p. 511. 

 f Quarterly Review, Dee. 1845, p. 106. 

 2 N2 



