1 8,' 5.] Animadversions on iH*. Hume, Wj 



not returned. This happened above 14 years ago, and conse- 

 quently was subsequent to M. Sage's experiments. Indeed, from 

 the letter to you, 1 have no doubt but Mr. R. Pliillips himself has 

 often committed the same blunder. 



That M. Bouillon-Lagrange did not benefit by M. Sage's 

 example as he might have done by mine, will be evident to Mr. 

 R. Phillips by the following sentence from Manuel d'un Cours de 

 Chimie : " Ce sel (nitrate de baryte) est utile pour reconnaitre la 

 presence de I'acide sulfurique. On pcut s'en servir pour separer 

 cet acide, qui se trouve quelquefois dans I'acide nitrique, et qui 

 empeche de I'employer dans de« experiences exactes." 



I shall select another case, out of a great many I could name : it 

 is that of Dr. Swediaur, who, as well as M. Bouillon-Lagrange, 

 must have been even personally acquainted with M. Sage, and. 

 could not be ignorant of the story of carbonate of barytes in the 

 acids, which may now be called Mr. R. Phillips's fable. In order 

 to divest nitrous acid of sulphuric acid, the Doctor prescribes the 

 following plan. Let a solution of nitrate of barytes be added until 

 there be no more precipitation, " donee nihil amplius praecipitetur." 

 I trust this experiment will be closely examined by Mr. R. Phillips, 

 and that he will favour your readers with the result, the nihil 

 amplius; and, for my own part, it is of no moment in this experi- 

 ment whether the acid contain sulphuric acid or not, for I will 

 venture to predict that the experiment will prove equally amusing 

 to Mr. R. Phillips or to any other operator. 



Discoveries and improvements in science invariably precede the 

 dates of their being presented to the public, depending on the dis- 

 position, convenience, and pursuits, of their authors, and various 

 other causes. In my own case these intervals have generally been 

 of many years, and that particularly of employing silver as a test 

 for arsenic, and asserting its superior efficacy, was not published 

 until above 20 years after I had discovered it. It occurred to me 

 while examining certain materials used in the pre))aration of car- 

 mine, and its utility was more distinctly evinced in subsequent 

 trials, es[)ecially while analyzing a metallic ore i)elonging to the 

 late Judge Bullcr. I might indeed appeal to many living witnesses 

 that I am not so forward to tease the public with my writings as Mr. 

 R. Phillips would insinuate. The Journals of the Royal Institu- 

 tion will bear testimony that I can prefer a private communication. 

 I am unwilling to bring names forward on this occasion without 

 permission of the parties ; but I can recollect one case in point, 

 and not unlike one of the experiments of M. Sage, which took 

 place more than ten years before my remarks on barytes were pidj- 

 lished. Few philosoj)hers have contributed more cHcctually to the 

 Philosophical Transactions than the Gentleman to whom I now 

 allude, and he jfrohabiy has not forgotten the short conversation that 

 passed in his library, at that time in the same street and very 

 near to my residence, on our inspecting a vessel containing car- 

 bonate of barytes in powder mixed with nitrous acid, and in a stato 

 of apparent ([uicscence. I am perbuadcd that this (jcntlenum did 



