J 3° Of the UNMETALLIC EARTH 



ingwhat has penetrated, impregnated, and formed 

 the faid earth, fo as not to become a bare (tone, 

 but an ore, and fuch a fort, as greatly refembles a 

 metallic, in particular, a grey, coppery, and fil- 

 very ore. Bifmuth-ore, which is greatly allied, 

 and adheres alfo to cobald, leaves behind, after 

 roafting, (in which operation it yields a femi-metal, 

 called bifmuth, or marcafite) an earth, or (lone, 

 called bifmuth ftone \ this earth, like that from co- 

 bald, affords a more beautiful (malt, but no me- 

 tal, in what manner foever treated. 



(3.) With refpect to the manner of exhibiting 

 this unmet allic earth in the pyrites, we fhall take no- 

 tice of each of the three principal forts of them, be- 

 ginning with the white, or arienic pyrites ; after fe- 

 parating the volatile portion of which, there remains 

 behind, in dole veflels, a reguline, femi-metallic 

 body, called fly ftone •, but in an open fire there 

 fublimes a grey, whitifh meal, ufed for mak- 

 ing arfenic, leaving behind it an earthy, or 

 ftoney fubflance, that looks greyifh, is very light, 

 and generally amounts to about \, Now, that in 

 this earth there is metal, nay, iron in particular, 

 cannot be denied, forafmuch as it is greatly at- 

 tracted by the magnet, and, in part, by means of 

 proper additions, may be brought to yield an iron- 

 regulus, nay, an iron-vitriol. But (1.) the iron is 

 in a variable proportion therein, whereas the pro- 

 portion of the entire fixed earth, with refpect to 

 the volatile part, comes pretty near to an equality. 

 I have remarked, that not only one fort of arfenic- 

 pyrites earth is more affected by magnetifm than 

 another \ nevertheleis, that it preferably turns to 

 iron, as I have had an in (lance of a fort from 

 Fahlun in Sweden. (2.) But this white-pyrites iron 

 is in a very fmall quantity, that is, icarce *V» in 



com- 



