300 HORNBLENDE SCHIST. 



beds. Such masses of greenstone can often be 

 proved to be, not only of later date than the pri- 

 mary rocks into which they intrude, but even to 

 be connected in some other part with the upper- 

 most of the secondary strata, or to be posterior to 

 these. But, by the same geologists, their affinity 

 being understood to be regulated by their posi- 

 tion, these substances have also been called pri- 

 mitive greenstone. Thus two rocks are con- 

 founded together which, in their origin and con- 

 nexions, are amongst the most remote ; and it 

 has consequently happened in geological descrip- 

 tions, drawn up by those who judge rather from 

 the nature of a rock than its connexions, that 

 serious errors have been committed. By limit- 

 ing the term greenstone to the trap family, such 

 errors are easily avoided or prevented. 



The objections to the term of greenstone 

 slate are not perhaps so strong, as the additional 

 word slate has not so often been used in discrimi- 

 nating any of the greenstones of the trap family. 

 But on account of the exact analogy subsisting 

 among these several rocks, in .each of these dis- 

 tinct families, and the total distinctness of the fa- 



