PREFACE. vii 



fee true, what a vaft variety of figures are 

 not thefe cryftals fubjeft to from a variety of 

 accidents? How many indeterminate and 

 confided cryftallizations reducible to no cer- 

 tain figure ? By how many external accidents 

 may not thefe figures, though originally per- 

 fect, be altered and modified ? What mall 

 we fay of his macfes or agglutinated cryf- 

 tals ? of the conic, fpheroidal, cilyndrical 

 ftiapes in which no angle can be difcovered ? 

 and of the various amorphous appearances of 

 moft Minerals ? 



Mr. Werner has endeavoured to claflifjr 

 Minerals by the joint confideration 'of all 

 their external properties, and yet, that even 

 this re-union is inefficient to determine their 

 nature, he hirnfelf gives us a clear proof in 

 his notes onCronfted, p. 217. There, on the 

 faith of thefe charadters, he ranges among 

 micas a green foliated fubftance, which, be- 

 ing fent to Mr. Bergman, proved to be a com- 

 pound of marine fait of copper and argilla- 

 ceous earth, though the quantity fent him 

 amounted but to one grain ; fo much furer 

 re chymical tefts ! Every icience muft be 

 founded on permanent principles. The only 

 principles of this fort that Mineralogy affords 

 are the relations of the bodies it conliders 

 with chymical agents. Without referring to 

 thefe, it can be reckoned at moil only a con- 



