33^ Tie Vitriol,^. 



But here it will be objected (i.) that fuch wa- 

 ters alfo hold an acid, and thus the alcali lies not 

 naked therein ; (2.) that we mud here mean not 

 an alcali prepared by fire, but a natural fort ; (3.) 

 that even in this formation of alum, an acid and al- 

 cali come, together, as when one conveys an acid 

 on fuch burnt ftone, and yet there no bitter fait, 

 here no alum is produced. As to the fir ft, it is 

 true, the alcali is not combined with, but (lands a- 

 part from the acid, which is (till joined with the 

 metallic earth, as was faid.. As to the fecond, the 

 axiom holds good, that we cannot form any juft 

 conclufions from what happens above the earth, or 

 by means of art, to what happens fpontaneouQy in 

 the bowels of the. earth: nor, converfcly, that what 

 happens not above the earth, or by art, may not 

 happen naturally under the earth, in certain cir- 

 cumftances, through length of time. Again, here 

 ferves the experience or obfervation of a calcarious 

 earth, or ftone, being not only corroded^ by, but 

 capable of being incorporated with bare water, 

 which fhall ftill remain clear and tranfparent : and 

 as to the third, in the inftance objected, the acid 

 is not firft produced or formed, but derived, as 

 already formed, from elfewhere ; whereas, in the 

 other cafe, it muft become fuch in the aft of alumi- 

 nifation t fo far, namely, as it arifes, without pyrites, 

 from the pure ftone abovememiontd. 



C II A P. 



