ARSENIATED COPPER. 



247 



lofophers ; and nothing can be pleaded in its excufe but the 

 revolution of opinion, which is apparently- read) to take place 

 in the theory of gafeous iluids. 



IV. 



Jieplj/ to the Ohftrvutions of M. VAbhS Hauy, on arfeniated Cop- 

 per. By M, LE CoMTE DE BouRNON, McmhtT of the 

 Royal and Linnean Societies of London.* \ 



IT is but a few days, Sir, fince I had the honour to receive Introduflory 

 from you the obfervations which you have made on the differ-''^ 

 ent fpecies of arfeniated copper, defcribed by me, in a memoir 

 on that fubjedt, read to the Royal Society of London, on the 

 19th of February, 1801. I have read thefe obfervations with 

 the greateft intereft, but not being able to adopt the opinion 

 refpedting (hem, to which the inveftigations you have fubnait^ 

 ted them have led you, I feel great obligation for liie oppor- 

 tunity you have afforded me of explaining myfelf more parti- 

 cularly than I have hitherto done, on what relates to this in- 

 terefiing fubjeft. Befides, you offer thefe obfervations with 

 that diffidence which ufually charaderizes real merit, accom- 

 panied with a doubt which calls for a new examination. 



You oppofe my opinion, Sir, on the divifion which I have 

 made of the arfeniated copper into four fpecies, with a deli- 

 cacy and a politenefs, which renders the llight mineralagical 

 difcuflion that becomes the neceffary refult of it, of infinite 

 value to me. It is very defirable that thofe fa6ts on which 

 differences of opinion may prevail (liould always be difcuffed 

 in this manner : the fciences would certainly gain by it, and 

 thofe who cultivate them would lofe nothing by yielding a lit- 

 tle to each other. 



Like you, Sir, when I employed myfelf on the fubflance Notice of the 

 which, fincethe firft elfays of the celebrated Klaproth on it, f^'J-^'^^'- ^"W- 

 has been called a combination of the arfenical acid and cop- 

 per, I thought it right to confider, under the fame point of 

 view, the different cryftalline forms which it offered, deriving 

 them all from one common bafe, and my firfl enquiries were 



* Tranflated from the original, communicated by the suthor. 

 For the paper of the Abbe, lee p. 187 of our prefent vol. 



dirccled 



