289 



promoting the reduction of metals, and in giving to them their 

 peculiar lustre, at a temperature even below that which the atmos- 

 phere ordinarily possesses*. 



Hence it appears probable, at least, that the formation of the 

 native sulphurets may take place, independent of the action of fire: 

 and M. Proust, and our celebrated countryman, Mr. Davy, are of 

 opinion, that the native sulphurets are actually formed, in conse- 

 quence of a similar decomposition of different solutions of metals, 

 by their combination with hydrosulphurets. It must, however, be 

 remarked, that some of the metals are not thus precipitated by the 

 addition of sulphuretted hydrogen alone ; since when the metals 

 are reduced to their minimum of oxygen, in consequence of its sub- 

 traction by the hydrogen, they retain the last portion of it with a 

 considerable degree 'of power, and are thereby prevented from en- 

 tering into union with sulphur. The addition, however, of an earth, 

 an alkali, or the carbonaceous matter, so abundant in the earth, 

 takes from the metal this portion of adhering oxygen, leaving it 

 pure, and free to enter into combination with the sulphur. Injus- 

 tice to the supporters of the Vulcanian theory, it must be also 

 remarked, that essentially different properties, both physical and 

 chemical, distinguish the pyrites, or native sulphurets, from the 

 artificial or factitious. Their crystalline forms, their peculiar splen- 

 dour, and their iridiscent investiture, yield matter, indeed, for per- 

 tinacious argument, on both sides of the question. But, surely, the 

 circumstance of these crystals being found, often, fast imbedded in 

 so combustible a body as bitumen, speaks strongly in favour of 

 their aqueous origin. Jet is frequently found containing them, or 

 being closely invested by them, and at the same time manifesting 

 no marks of having been acted on by heat ; which would surely 

 have been the case, if their formation, which must have been at the 



* An Essay on Combustion, by Mrs. Fulhame, p. 178. 

 VOL. I. P P 



