H8 a s y s t e m O f 
a. With the acid of common fait, Atcati 
miner ale volatile acido falis unitiim, Na-- 
live fai ammoniac, Sal ammoniacum 
tivum^ Sed..cxxxli 
SECT. CXLIL 
2 . With earths. 
a. Clay, Alcali minerale ^Volatile argiltd 
mixtim. 
The greatefl: part of the clays contain a 
volatile alcali, which difcovers itfelf in the 
diftiilation of the fpirit of fea-falt, &c. f 
If that hypotheiis could be proved true, which holds that 
volcanos and fubterranean fires arife from flates, formed from 
vegetables, animals, and the humus aUr or mould, mixed toge-* 
ther, (Seft. cxxiv.) the origin of the fal ammoniac at Solfa- 
tara would eafily be acknowledged ; lince we know that pe» 
trifadions difcover a principle within them, which contains 
the fal urinofum* 
t in cafe fome of the clays are produced from the mould or 
huinus ater (Se6l. 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 pre- 
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 fiiew, and by rational experiments. 
A German author has lately afferted, that metals, accord- 
ing to his experiments j have been found difiblved or minera- 
lifed by a volatile alcali ; but, befides that fome fubjefls men- 
tioned by him ; for inllance, the Simple, or Red Chalk ; the 
Humrarian Gilben, or Vein Stones ; and the Horn Silver ore ; do 
not fhev/ the leall mark of it ; there is alfo wanted a deferip- 
tion of the experiments he has made, and of the phoenomena 
which have prefented themfelves to him, during the examina- 
tion of the other ores which he has mentioned : for thefe res- 
ions his opinion cannot yet be admitted. 
SECT, 
