more than simple modifications of one and the same power, origi-
nally belonging to matter ; but he maintains, at the same time, that
these modifications certainly exert as much force, at the time of their
operation, as could be exerted by attractive forces that are really dif-
ferent.
In the third part, which treats of the different kinds of sulphuret of copper, we are first apprised of the importance of this inquiry, by the observation, that, on comparing the different characters of this substance with those of the triple sulphuret described in the first part of this paper, we shall find that the antimony and the lead, which have been generally considered as constituent parts of the last-men- tioned ore, are, in fact, nothing more than accidental ingredients, introduced merely by the attraction of aggregation.
In the sequel of the paper, the author introduces an ample stock of observations and analyses respecting various cupro-sulphurets, which have been hitherto very imperfectly examined. And first he treats of the gray tetrahedral sulphuret of copper, which is found to consist of copper, iron, and sulphur, in different proportions; the gray copper ore, called Fahlerz by the Germans, being of the same composition. The yellow copper ore, or Kufi'm-kies of the Germans, appears to be double sulphuret of copper and iron, but constthng a species distinct from the gray sulphuret of the same tetrahedral form. Among these, there is one in particular which has not yet been described as belonging to this ore; namely, the dodecahedron with rhombic planes, which has hitherto been found only in Com- wall, and there only in small quantities, though in crystals of con- siderable size. It is also shown at length wherein most of the cha- racters of the tetrahedral yellow cupro-martial sulphuret differ from those of the octahedral sulphuret of iron.
The following question is next proposed, and strongly recommended to the future investigation of mineralogists. As the true sulphuret of copper and the fahlerz are of a blackish gray colour, how comes it that the kindof cupro-martial sulphuret, commonly called pyritical copper,_ has always that brilliant yellow colour which particularly characterizes it, and which is the principal cause that leads many mineralogists to consider it as being nothing more than a martial pyrites mixed with copper? The solution of this difficulty, we are told, will materially contribute to ascertain the external characters of this kind of sulphurets.
’l‘he cupro—martial sulphuret, called by Werner Buntlcupfererz, is a new species of this ore, which crystallizes in forms that are peculiar to it, and not at all analogous to those of the other cupro—martial sulphuret. The ingredients, which are solely copper, iron, and sul- phur, difi‘er considerably in their proportions in different specimens.
The author desires that what he has here said may be considered merely as a cursory account of some of the sulphurets of copper, from which, however, he thinks it maybe inferred, that there exists a great number of species of this substance which have not yet been de-
