COLL. MINERALS. 69 



forms a large portion. Yet there are no rocks of the trap 

 family in this island, if we except veins, to justify the 

 notion that it is in its native place. 



These veins are by no means common, but they may be 

 seen in different places. Their dimensions, as far as I 

 observed them, do not exceed four or five feet, arid they 

 are formed of a black compact basalt. They are often 

 characterized by a tendency to the columnar fracture, and 

 do not seem materially to disturb or influence the rocks 

 which they traverse. 



