OVERLYING ROCKS. 487 



it is generally of a green colour. At times it pre- 

 dominates so as almost to exclude the other ingre- 

 dient. In certain cases, it is, like hornblende, 

 sparingly dispersed throughout the rock, the clink- 

 stone or compact felspar predominating ; and, in 

 these examples, the mixture resembles the sye- 

 nites, as already remarked : in others, it becomes 

 so minutely subdivided, and the rock puts on an 

 aspect so nearly homogeneous, that it can scarcely, 

 if at all, be distinguished from basalt. This com- 

 pound is here only distinguished by the general 

 term of augit rock, but it may be a question whe- 

 ther it would not be convenient to adopt terms ap- 

 plicable to its several varieties, so as to correspond 

 to the three analogous rocks into which hornblende 

 enters. In this case an adjective term might be 

 employed with less inconvenience, and with a 

 slighter change of nomenclature than a new name ; 

 and we should then have augitic greenstone, 

 augitic syenite, and augitic basalt. But this is a 

 subject for the consideration of mineralogists. 



The next mineral occupying a place analo- 

 gous to that of hornblende, is hypersthene. The 

 circumstances under which it is found, are so 



