of the magnetical Pyrites , &c. 329 
distilled with sulphur, (due attention being paid to the degree 
of heat,) the product is found to have assumed most of the 
chemical and external properties of the natural common pyrites, 
density alone being excepted. 
The application of the above observations, to the principal 
subject of the present Paper, is sufficiently obvious ; for, when 
it is considered, that the magnetical pyrites is so different from 
the common pyrites, in colour, hardness, solubility in sulphuric 
acid, and more especially in muriatic acid, with the copious 
production of sulphuretted hydrogen gas ; when, by analysis, it 
has been found to consist of 36 or 37 of sulphur, combined with 
about 63 of metallic iron; and, when the artificial sulphuret 
of iron which has been lately described, is proved to agree with 
the magnetical pyrites in the nature and proportions of its com- 
ponent ingredients, and in every one of the abovemention ed 
properties ; it is evident that the magnetical pyrites is identically 
the same with this sulphuret, which hitherto has remained un- 
discovered in nature, and has only been known as a product of 
our laboratories. In order however more fully to satisfy myself, 
I made experiments on the artificial sulphuret, which I formed 
with sulphur and fine iron wire. 
This substance agreed, in all the properties which have been 
noticed, with the magnetical pyrites ; and the precipitates ob- 
tained by adding prussiate of potash, and ammonia, to the 
muriatic and sulphuric solutions, were precisely similar. The 
specific gravity was 4390, whilst (as I have already remarked) 
4 hat of the magnetical pyrites is 4,518. 
tJ u a 
