HORNBLENDE SCHIST. 301 



milies themselves, it seemed prudent to avoid the 

 use of a term, which, while it is unnecessary, 

 might also be a source of confusion. One of the 

 principal objects in view in this arrangement, 

 has been to facilitate geological descriptions and 

 to diminish the ambiguity arising from a misap- 

 plication of terms. In describing rocks for any 

 other purposes, it is still in the power of those 

 who prefer the use of the terms which have been 

 rejected, to have recourse to them ; as they are, 

 with this view, most commonly mentioned in the 

 catalogues of varieties. 



Hornblende schist rarely occurs indepen- 

 dently, or in such a manner as to form extensive 

 tracts without the interference or alternation of 

 some other primary rock. The only large mass 

 of this nature known to me, forms the mountain 

 of Ben Lair in Ross-shire. 



It is most commonly associated with gneiss, 

 and generally in strata of very moderate dimen- 

 sions, often of great tenuity. This association 

 is so intimate, and, in many instances, the horn- 

 blende schist is in so small a proportion to the 

 gneiss, that it has been considered a subordinate 



