€o Mr. Smithson on the Composition of the 
dissolved in the precipitating and washing waters, was scru- 
pulously collected. 
The importance of a knowledge of the true quantity in 
which matters combine, is too evident to require to be dwelt 
upon ; but this importance will be greatly augmented, if it 
should prove that this quantity is, as has been suggested, ex- 
pressive of the forces with which they attract each other. It 
is perhaps in the form of matters that we shall find the cause 
of the proportions in which they unite, and a proof, a priori, of 
the system here maintained. 
I have examined some of the grey ores of copper in tetrae- 
dral crystals ; but the notes of my experiments are in Eng- 
land. I can, however, say, that they do contain antimony, and 
that they do not contain iron in any material quantity. With 
respect to the proportions of the constituent parts, I cannot 
now speak with any certainty ; but, I think, that at least some 
species of fahlertz contain a smaller portion of sulphuret of 
antimony, than the fahlertz does which exists as an element 
in the foregoing compound one. 
Of the Form of this Substance. 
Of the seventeen figures which have been given, as of the 
crystals of this compound sulphuret, in Part II. of the volume 
of the Transactions for 1804, great part are acknowledged to 
have no existence, nor are indeed any of them consistent with 
nature. 
This substance seems to have yet offered but one form, and 
