3 26 Mr. Hatchett’s Analysis 
The pyrites crystallized in regular figures,, such as cubes and 
dodecaedrons, according to the above analyses, contain less 
sulphur, and more iron, than the radiated pyrites, and perhaps 
than others which are not regularly crystallized. This difference, 
however, is not considerable ; for the dodecaedral pyrites, which 
afforded the smallest quantity of sulphur of any of the regularly 
crystallized pyrites, yielded 52.15; and the radiated pyrites, 
No. 5, gave 54.34; the difference, therefore, is only 2.19. So 
that the mean proportion of sulphur, in all the pyrites which 
were examined, is 53.24 per cent, and, taking the proportion of 
sulphur in the magneticaf pyrites at 36.50 or 37, the difference 
between this and the mean of the common pyrites will be 16.74 
or 16.24. The magnetical pyrites, therefore, is quite distinct, 
as a sulphuret of iron, from the common martial pyrites ; and* 
in The following observations I shall prove, that a sulphuret 
consisting of the proportions last mentioned, has till now been 
unknown as a product of nature. 
§VI. 
Although pyrites is one of the most common of mineral 
substances, yet the discovery of its real nature is comparatively 
of a late date; for it appears, that even Agricola (whose know- 
ledge of mineral bodies was certainly great, considering the state 
of science in his time) was not acquainted with its characteristic 
ingredient, namely, iron. According to Henckel, this was first 
noticed by our countryman Martin Lister, a member of this 
learned Society, who says “ Pyrites purus putus Jerri metallum 
“ est” 
From the time of Henckel, pyrites seems little to have 
attracted the notice of chemists, until Mr. Proust, the learned 
