SERPENTINE. 245 



culiar character, which is noticed in the synopsis 

 of that rock. When they occur in contact with 

 limestone, the two substances are frequently 

 much intermixed ; veins of the carbonat of lime 

 penetrating the serpentine, or fragments of both 

 being confusedly blended together. When the 

 contact is that of hornblende rock with serpen- 

 tine, a perfect gradation between the two can 

 sometimes be traced. 



There is one interesting situation, in the 

 secondary class, in which serpentine occurs, al- 

 though two examples only of it have fallen under 

 my notice, and it has not been observed by other 

 geologists. In both these cases, veins of trap 

 pass through strata of secondary limestone, and 

 where the vein is in contact with the limestone, 

 it changes its character and becomes a serpen- 

 tine, while it also contains, in those parts, the 

 minerals usually found in that rock, namely, 

 asbestos and steatite. The limestone, at the 

 planes of contact, also contains steatite ; and thus 

 a species of irregular gradation becomes esta- 

 blished between the trap and the limestone. The 

 gradation from the serpentine to the trap, within 



