[ i8 7 3 
As foon as the attraction between the copper and 
the acid ceafes, the mutual attraction between the 
minute particles of the metal prevails, fo as to form 
large folid maffes at the bottom of the pits, nineteen 
twentieths of which are pure copper. Thefe folid 
maffes are partly occafion’d by the preffure of the 
incumbent heap of granulated copper, conftantly in • 
creafing. 
Hence we fee, that the art of effaying, or fepa- 
rating metals from their ores, chiefly confifts in eva- 
porating an acid, which prevents the mutual attrac- 
tion of the metallic particles ; for when the acid is 
driven off by the violence of fire, the particles fall 
into their proper fphere of attraction, and affume a 
folid form. 
From what has been offer’d on the theory of this ad- 
mirable procefs, feveral practical hints may be taken 
to render fuch fprings more profitable ; and perhaps 
an eafier method may be difcover’d of feparating cop- 
per from its ore, by precipitation, than by calcina- 
tion. But fuch improvements I refer to tnofe more 
converfant in the practice of metallurgy. 
Having, I hope, given a fatisfaCtory account of the 
effeCts of this water on iron, and proved, that it is owing 
to a ftrong mineral acid, which it contains, I fhould 
next inquire into the fource of this acid •, but am an- 
ticipated in that conjectural refearch by many inqui- 
fitive gentlemen, who have penetrated deeper into the 
bowels of the earth, and difcover’d, or rather taken 
for granted, a vague acid, which, they fay, is dif- 
fufed thro’ the whole mineral kingdom, and being 
united with different mineral fubftances, forms vitriols 
of different kinds. This hypothefis appears the more 
A a 2 probable. 
