MULL. GEOIOGY. 563 



marked by the peculiar form of the shell, although these 

 species have not as yet all received distinct names from 

 conchologists. 



The trap veins that traverse these strata are in general 

 so far parallel to them as to have the appearance of beds ; 

 but their real nature is detected by their occasional inter- 

 ference, and by the numerous ramifying veins which they 

 send into the adjoining limestone. 



The distant view of this shore, characterized as it is 

 by its flatness for a considerable space inland, naturally 

 leads the geologist to expect that the whole is formed 

 of secondary strata ; particularly as all the other parts 

 of the island which consist of trap are hilly, if not moun- 

 tainous ; and he is not a little Disappointed to find even 

 the flattest parts composed of the overlying rocks through- 

 out their whole extent. 



The last portion of the secondary strata which came 

 under my notice consists of sandstone, and is found on 

 the western shore of Gribon, being most remarkable at 

 that part which lies opposite to Inch Kenneth. The 

 reader is prepared to understand the appearance and 

 position of these strata from the description already 

 given of that island. They are found there lying on 

 the elevated edges of the primary strata, in the position 

 called unconformable. This is also the case in certain 

 places under Gribon; but the rule is not universal, and 

 as the position of this secondary rock in relation to the 

 primaiy is material in a general view, it is illustrated 

 by a diagram.* 



It will be seen by this diagram that the strata are 

 here horizontal, or nearly so, above, and they would thus 

 be considered, like those of Inch Kenneth, unconform- 

 able, could no further view of them be obtained, since, 

 were they prolonged, they would occupy a similar posi- 

 tion. But if they are examined at a lower point, they will 



* Plate XX. fk. 10. 



