HORNBLENDE SCHIST. 299 



same characters as hornblende schist ; and, that 

 if it is ever deficient in the schistose structure, 

 the limits are evanescent. Further, the rion- 

 schistose varieties of this rock, are always inter- 

 stratified with the other schistose rocks which 

 they accompany, commonly in their beds ; while, 

 where numerous alternations occur, as is gene- 

 rally the case, some of the beds will be found 

 deficient in the schistose structure, while others 

 possess it in different degrees. Lastly, the same 

 bed will, in one part of its progress, present a 

 laminar or schistose, in another an uniformly mas- 

 sive structure. 



The term primitive greenstone is applied to 

 this rock whenever it consists of an intermixture 

 of felspar and hornblende, and is not schistose ; 

 not very correctly, since, in almost every case, 

 the felspar is either red or white, and the horn- 

 blende black. But the chief objection to its use 

 is the following. The greenstone of the trap fa- 

 mily is often found in the form of veins intrud- 

 ing 1 into the primary as into the secondary strata ; 

 and, in a few instances, these veins are so far pa- 

 rallel as to admit of being confounded with real 



