2.58 RASAY. GEOLOGY. 



another part of this work, and which I have distinguished 

 by the name of augit rock, to separate it from the common 

 greenstones with which it has often been confounded. 

 It contains, in addition to these ingredients, prehnite ; 

 sometimes dispersed in small globular concretions so as 

 to form a constituent part of the rock, in other cases 

 distinctly placed in cavities and imperfectly crystallized. 

 This prehnite is most commonly of a white colour, rarely 

 inclining to very pale green. I discovered no other 

 independent mineral in Rasay. 



Veins of trap occupying the usual positions occur 

 in different parts of the island, but more rarely than 

 would be expected, when we consider their abundance 

 in Sky, and the vicinity of the great masses of trap 

 in that island, in the neighbourhood of which they are 

 commonly so predominant. They seemed no where 

 to present any appearances sufficiently remarkable to 

 be worthy of record. 



