ON ARSENXATED COPPER. i QY 



lated concretions as iimple varieties of the acute odlahedron, 

 fince he indicates the intermediate modifications which con- 

 ned thefe varieties with their type ; fo that, according to him, 

 there are cryftals which are perfe6tly determined in one part of 

 their length, and fibrous at their extremity. 



M. de Bournon, doubtlefs ftruck with the ex<?feption which A fifth fpedes 

 the agreement between the two fciences, announced by Mr. 

 Chenevix and hinifelf, (eemed liable to, in this inflance, has 

 fince inferted in Mr. Nicholfon's Journal * a note, in which he 

 propofes to efiabiiQi a fifth fpecies of arfeniated copper, 

 compoled of the capillary cryflals and mammellated niafTes, 

 which feems to operate lefs in removing the difficulty than in 

 bringing it to light. 



It cannot be denied that the modifications of arfeniated cop- External differ- 



per offer fenfible differences in their afped, their exterior ^""/ ftould 

 r 1 ,, ■ 1 1,^ 1 Ti ir ■ ,- r not be admitted 



lorms, and their colours. M. de Jtsournon alio indicates lome alone as evidence 



in their hardnefs and in their fpecific gravities. But the ''^ ^. '^'^^'■^"'^ 

 redu6lion of natural beings to the fmallefl; poflible number ot 

 fpecies, really difiind, is an advantage of fuch value to fcience, 

 which it perfedionates by fimplitying it, that, before feparating 

 fubftances, according to thole diverlities which feem to be at 

 variance with the relations which they otherwife have, and be- 

 fore feeking particular fpecific names for them, which would 

 be neceffary, all the means of afcertaining that the diverfities 

 inqueftionare not purely accidental, (hould be exhaufied. Even 

 though the refearches which ftill remain to be made for the 

 accomplifhment of this objed, lliould have no other effed but 

 to caufe the difappearance of one fingle fpecies, admitted by 

 the two celebrated men whole refults I have let forth, from 

 the fyflem, they will not be unprofitable to the progrefs of 

 mineralogy. 



*^* A reply communicated by the Count de Bournon will 

 appear in our next. 



* Philofophical Journal, new Series. Vol. VII. p. 577. 



Ob/ervatipns 



