306 HORNBLENDE SCHIST. 



ture, however, depend on the laminar and on the 

 granular crystalline dispositions of the parts. In 

 the former case, the rock is always, and neces- 

 sarily, either laminar or schistose ; but, in the 

 latter, it is not necessarily the reverse ; a similar 

 fissile disposition being produced by the manner 

 in which the crystalline particles are arranged. 

 In those cases where, to a granular texture, there 

 is superadded a massive or non-fissile disposition, 

 it forms that which has been already mentioned as 

 constituting the hornblende rock of many geolo- 

 gists. 



Whatever appearance of a mechanical dispo- 

 sition, may arise from the occasional laminar al- 

 ternation of the ingredients of this rock, it is un- 

 necessary to make any remarks on it, as they 

 would only be a repetition of the doubts already 

 stated under the head of micaceous schist. It ig 

 barely necessary to observe, that the texture ap- 

 pears to be truly crystalline, or chemical, in all the 

 varieties; and that it has not hitherto presented 

 any, containing, like micaceous schist, decided 

 fragments of other rocks. 



The minerals essential to hornblende schist, 



