170 Count de Bournon's Description of 
aspects under which it exists, in the county of Cornwall, may 
entitle it to be considered as one of the many mineral sub- 
stances which are peculiar, or nearly so, to England. 
Of the various works on mineralogy lately published, there 
are few which have not mentioned arseniate of copper, among 
the ores of this metal. It seems, however, that some of their 
authors had no knowledge of this ore, except from the very im- 
perfect account communicated by the celebrated Klaproth, in 
1 787, in the Schriften der Gesellschaft Naturforscbender Freunde , 
Voi. VII. in which he has given an interesting sketch of the mi- 
neralogy of the county of Cornwall, as far as it was then 
known. Others seem to have possessed only imperfect speci- 
mens of arseniate of copper, as none of the forms which they 
attribute to its crystals, can belong to it. Besides, they all 
confound with this ore, those cubic crystals, of a very beau- 
tiful green colour, which are found in Muttrell mine, contiguous 
to Huel Gorland mine ; and which, according to the analysis 
made with the greatest care and ability, by Mr. Chenevix, 
are of a nature totally different, and cannot properly be classed 
among copper ores, as they contain but a very inconsiderable 
quantity of that metal. 
The existence of arseniate of copper seems, however, even 
at this day, to be an object of doubt among the French mine- 
ralogists ; for the Abb4 Hauy does not mention it in the 28th 
and following numbers of the "Journal des Mines , although they 
contain an interesting extract of a system of mineralogy, which 
he was then preparing for the press ; nor has M. Fourcroy 
even hinted at it, in his Systeme des Connoissances Chimiques, 
lately published. 
It is now above twenty years, since arseniate of copper was 
