498 Notices and Extracts from the Minutes of the Geological Society. 



Lastly, the author comjjares the relative connexion of igneous deposits with 

 metallic accumulations, and states that ores are more abundant in granite, 

 certain porphyries, syenites, amygdaloids, and trap, which he calls underlying, 

 unstratified rocks, than in the newer porphyries, the dolerites, and the true 

 volcanic formations, which he distinguishes by the term of overlying, unstra- 

 tified rocks ; and he alludes to the assistance which the practical miner would 

 derive from attending to this distinction, as well as to the principal object of 

 the paper, — the connexion of igneous with metalliferous deposits. 



