148 A S Y S T E M O F 



a. With the acid of common fait. Aleak 

 miner ale volatile acido [alls unitum. Na- 

 tive fal ammoniac, Sal ammoniac urn na- 



tivu;n, Sect, exxxii *. 



SECT. CXLII. 



2. With earths. 

 a. Clay, Alcali miner ale volatile argilLl 

 mixtum. 

 The greater! part of the clays contain a 

 volatile alcali, which difcovers itfelf in the 

 diftillation of the fpirit of fea-lalt, &c. f 



* If that nypothefis could be proved true, which holds that 

 volcanos and fubterranean fires arife from flates, formed from 

 vegetables, animals, and the humus- ater or mould, mixed toge- 

 ther, (Sect, exxiv.) the origin of the fal ammoniac at Solfa- 

 tara would eafily be acknowledged ; fince we know that pe- 

 trifactions difcover a principle within them, which contains 

 the fal urinofum, 



*T In cafe fome of the clays are produced from the mould or 

 humus ater (Sect, xci..) it is not difficult to fee the reafon of 

 the prefence of this alcali in them ; but, though it would be 

 both ufeful and curious to know all the changes of minerals, 

 yet it is much better to take and employ them in their jke- 

 fent ftate, than to lead the mind into perplexities by examin- 

 ing the combinations of thefe things by other means than 

 by what the external fenfes ihew, and by rational experiments. 



A German author has lately afferted, that metals, accord- 

 ing to his experiments, have been found diffolved or minera- 

 lifed by a volatile alcali ; but, befides that fome fubje&s men- 

 tioned by him ; for inftance, the Sinople, or Red Chalk ; the 

 Hungarian Gilben, or Vein Stones ; and the Horn Silver ore ; do 

 not fhew the kaft mark of it ; there is alio wanted a defcrip- 

 tion of the experiments he has made, and of the phcenomena 

 which have prefented themfelves to him, during the examinar 

 tion of the other ores which he has mentioned : for thefe rea- 

 fons his opinion cannot yet be admitted. 



SECT. 



