triple Sulphnret, of Lead, Antimony, and Copper, &c. 61 
described; also, that several of those with which we are ac- 
quainted, have not been sufficiently examined. These sulphurets 
are well worthy of fixing the attention of chemists. The obser- 
vations to which they may give rise, are sufficiently interesting 
to engage their attention, and induce them to bestow particular 
care on their inquiries concerning them, as such inquiries may 
perhaps tend to increase our knowledge respecting the nature of 
copper, and also of iron. But I cannot too strongly recommend 
to those chemists who may engage in the research, to be very 
particular in the choice of the specimens they make use of, and 
also to make a great number of experiments, that they may 
serve as objects of comparison to each other. 
Having very favourable opportunities of examining, and com- 
paring with each other, the different kinds of copper ore that 
are found in the county of Cornwall, (which county furnishes a 
greater variety of combinations of that metal than any other part 
of Europe, several of which are peculiar to it, j it was impossible 
that my attention should not be attracted by the many in- 
teresting facts that came under my observation. Next to the 
combinations of this metal with the arsenical acid, the study of 
its sulphurets has been the principal object of my pursuits ; and, 
if future circumstances should concur with my wishes in that 
respect, I hope I shall have it in my power to present to the 
public the result of my observations on those sulphurets. 
Those observations will, I trust, furnish additional proofs of 
the truth of a circumstance respecting which I have long ceased 
to have any doubts, and which I have already, on various occa- 
sions, (particularly in my description of the arseniates of cop- 
per,) attempted to establish, namely, that there exist many 
minerals, which differ in species, although they have the same 
