COMPACT FELSPAR. 375 



have been sufficient to justify the present arrange- 

 ment, even without the much stronger reasons 

 afforded by these essential differences in the 

 geological characters of this substance as it occurs 

 in the primary and secondary classes. 



If there are transient and occasional differ- 

 ences in the specimens of this rock as they are 

 found in these two distinct situations, they are 

 not such as to form a permanent or effectual dis- 

 tinction between the two ; while the analysis of 

 both, presents, as far as is yet ascertained, the 

 same remarkable peculiarities. 



Compact felspar contains potash and soda 

 united to the other earths that form its principal 

 ingredients ; and both these alkalies are found 

 in it, in whatever situation it exists ; proving that 

 it is radically, as well as ostensibly, the same 

 substance in both cases. By this analysis, no less 

 than by its general characters, it differs essen- 

 tially from common felspar, which contains pot- 

 ash only. Were it either easy or adviseable to 

 change a name long received, this is one, as al- 

 ready hinted, by the reformation of which the 

 mineralogical nomenclature might acquire an 

 advantage. But, as in many other cases, where 



