374 

 COMPACT FELSPAR. 



THE present substance offers an example of 



those difficulties which beset all attempts to make 



an unexceptionable arrangement of rocks. It is 



now also, for the first time, admitted to a place 



among these ; a practice justified by the space 



which it so often occupies among them, and by 



the peculiar connections in which it is found. 



To have considered it as a modification of gneiss, 



would have produced still greater irregularity ; 



and, to have omitted it, would have left a blank 



not atoned for by finding it enumerated by mine- 



ralogical writers in their catalogues of simple 



minerals. 



Compact felspar occurs also in another part 

 of this arrangement, in a very conspicuous man- 

 ner, both in irregular masses, and in veins, form- 

 ing a member of the great family of overlying 

 rocks. The student who finds it constituting 

 an integrant part of the series of gneiss, might 

 therefore be misled, were it not here shown to 

 exist also as a primary and stratified rock, of the 

 same age and date as this antient member of the 

 primary strata. The example of limestone would 



