IIYPERSTIIENE ROCK. 



27 



NlrrLE Top. 



Dix's Peak. 



View from Clear Pond, looking towards the northeast, from a sketch tty R. C. Taylor. 



.MlCu.MBE'S MOINTAIN. 



2. Hypersthene Rock. 



Composition and varieties. — Imbedded minerals. — Topographical details. — Effects of frosts, rains, ^c. — Scenery. 



The rock which I have denominated Hypersthene Rock, is essentially composed of labra- 

 doriie, or Labrador feldspar and hypersthene in very unequal proportions, the former consti- 

 tuting by far the largest part of the mass. Like other primary rocks, however, its constitution 

 is not fixed ; the materials not onlj^ varying in proportions, but also in kind, particularly as it 

 regards the presence of one of the elements. Thus, the hypersthene may disappear, and be 

 replaced by hornblende or pyroxene, or other clianges equally important may take place, 

 without affecting essentially the character of the rock. The labradorite, however, is always 

 present in the mass which has received this designation ; and it is this specific mineral which 

 really gives character to the rock, though the contrary appears from the use of the term 

 hypersthene. This discrepancy arises from following the usages and customs which are 



