5S 



ILLUSTRATIONS OF THE 



infolubility of the fubflances that fill the veins 

 in any one menftruum whatfoever ; from the 

 total difappearance of the folvent, if there was 

 any ', from the complete filling up of the vein by 



w 



the fubflances w^hich that folvent had depofited; 



appearances 

 ; and, laftly, 



from th 



abfence of 



the 



f horizontal or gradual depofit 



fro 



the 



Hence of clofe cavities, lined 



cryftals, and admitting no egrefs to any thing 

 but heat. 



+ 



50. To the fame effed may be mentioned thofe 

 groups of cryftals compofed of fubftances the 

 moft different, that are united in the fame fpe- 

 cimen, all interfetSling and mutually impreffing 

 one another. Thefe admit of being explained, on 

 the fuppofition that they vt^ere originally in fu- 

 fion, and became folid by the lofs of heat ; a 

 caufe that aded on them all alike, and alike im- 

 pelled them to cryftallize : Bat the appearances 

 of fimultaneous cryftallization feem incompati- 

 ble with the nature of depofition from a folvent, 



r 



Avhere, with refped to different fubftances, the 

 effeds muft take place flowly, and in fuccelfion. 



51. The metals contained in the veins which 



appear very commonly 



we are now treating of, 



the form of 



d by fulpl 



Thei 



ith th 



fubft 



be 



produced, as we know, by heat, but hardly by 



the way of folution in a menftruum, and cer- 

 tainly 



