MINERALOGY. 149 



SECT. CXLIII. 

 Observations on Salts. 



The perfect knowledge of thefe bodies muft be 

 had from chemical books and practical chemiftry, 

 being almoft the chief fubject of that fcience. 

 From thence we likewife learn why the acids are 

 coniickred as falts, though a certain figure nei- 

 ther is found, nor can reafonably be expected in 

 them. We are farther taught, that the angular 

 figure, which is fuppofed to be eiTential to falts, 

 and by its varieties to mark out their different 

 fpecies, depends on an alcali, earth, and metals, 

 united with more or lefs water : for elfe, if this 

 was not fo, the criftal of alum and vitriol ought 

 to be of the fame figure, no nitrum cubicum would 

 exifl, nor could any criftallifation happen in fuch 

 cafes, where the acids neccffarily muft be parted 

 (Seel. xi.). 



Salts are contained in all the three kingdoms of 

 nature; and as it is not yet known how the changes 

 happen, and how far the varieties depend on one 

 another, we cannot attribute to the mineral 

 kingdom any other falts than thofe which are 

 found truly changed in the earth. 



The ufe of the falts in medicine and in com- 

 mon life is fo great, that it would require a fepa- 

 rate treatife, if it were to be fully difcufted. Mean 

 while, every one who applies himfelf to the ftudy 

 of mineralogy, in order to learn the ufe to which 

 the mineral bodies can be employed in common 

 life, I mean in particular mines, muft endeavour 

 to difcover where falts may be found, and how 

 they muft be prepared, fo as to be bell lit for ufe. 

 But the preparation of falts is not the fubject of 



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