SLiCNETtCAL tY&lTES/, 273 



difference in the proportions of their component ingredients ; 

 but, as the retails are the average of feveral experiments, I 

 have not any reafon to doubt their accuracy. 



The pyrites cryftallized in regular figures, fuch as cubes Regular cryflals 

 and dodecaedrons, according to the above analyfes, <-' onla ' n "'^'"ron thaa 

 lei* fulphur, and more iron, than ihe radiated pyrites, and other pyrites. 

 perhaps than others which are not regularly cryftallized. This 

 difference, however, is not confiderable ; for the dodecaedral 

 pyrites, which afforded the fmaileft quantity of fulphur of 

 any of the regularly cry ftallized 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 fuU 

 phur, in all the pyrites which were examined, is 53/24 per 

 cent, and, taking the proportion of fulphur in the magnetical 

 pyrites at 36.50 or 37, the difference between this and the 

 mean of the common pyrites will be 16.74 or 16.21-. The 

 magnetical pyrites, therefore, is quite diftinct, as a fulphuret 

 of iron, from the common martial pyrites ; and, in the follow- 

 ing obfervations I fhall prove, that a fulphuret coniifling of 

 the proportions laft mentioned, has till now been unknown 

 as a producf of nature. 



§ VI. 



Although pyrites is one of the moll common of mineral Hiftory of py~ 

 fubftances, yet the difcovery of its real nature is comparatively ntCi ' 

 of a late date ; for it appears that even Agricola (whole know- 

 ledge of mineral bodies was certainly great, confidering the 

 flate of fcience in his time) was not acquainted with its cha- 

 racteriftic ingredient, namely, iron. According to Henckel, 

 this was firft noticed by our countryman Martin Lifter, a 

 member of this learned Society, who fays, " Pyrites purus 

 putusfcrri metullum eft." 



From the time of Henckel, pyrites feems little to have Experiments of 

 attracted the notice of chemifts, until Mr, Prouft, the learned Prouft * 

 profelfor of chemiflry at Madrid, publifhed two memoirs, in 

 which he dates, that there are two fulphurets of iron, the one Two fulphuret* 

 feeing artificial, and the other natural. The firft is the fulphu-° f i ron '; . ar u ti . fi " 



° '.■•., * Cial, which is 



ret which is formed in laboratories, by adding fulphur to red- eafily foluble in 



hot iron, or by expofing both of them to heat in a retort. This acid3 > and n:Ua ' 

 ..-. •„ , ,• ? ,- , ,- , , ,,.,., "'» lets foluMe. 



is diftmguifned from the (econd fulphuret, (which is the com- 

 mon martial pyrites,) bv its eafy folubi'ity in acids, efpecially 

 Vol. X.— April, 1305. T in 



