466 SANDY ISLE. - GEOLOGY. 



its height and of a steeple-like form, while the other 

 resembles a huge tower. They are seen to great advan- 

 tage in gales of wind x when the high mountains of Rum 

 are involved in clouds and the tide of this rapid strait 

 is breaking on the shores ; circumstances indeed always 

 peculiarly appropriate to the wild features of these rocky 

 coasts.* 



The general alternations of the trap with the conglo- 

 merate are more visible in Sandy isle than in Canna ; and 

 it is much more easy to trace the beds of coal and shale. 

 But there is one peculiar circumstance here in the dispo- 

 sition of the conglomerate, which is worthy of remark : 

 it occurs in the steeple-formed rock above mentioned. 

 That substance is here divided from the solid trap by 

 a vertical, instead of a horizontal line ; the one side of 

 the mass being constituted of the former, and the other 

 of the latter. In other respects the substances and their 

 connexions are precisely the same as in Canna, or in the 

 other parts of this island where they lie in a horizontal 

 position.f It is not easy to explain this appearance ; 

 but it is not impossible that the whole mass has been 

 thrown down from a superior position, into that in which 

 it now stands; as there are no symptoms of a similar 

 general disturbance in the island itself, and it is not 

 conceivable that the conglomerate should have been 

 deposited in its present position in one limited spot 

 only. 



Sandy isle, like Canna, presents examples of a circum- 

 stance rare in the Western islands ; namely, loose frag- 

 ments of a different rock from that of which it is formed, 

 lying on the surface. These are large blocks of red 

 sandstone, somewhat rounded; and they are found in 

 considerable abundance on the flat shores of both. They 

 are not to be seen in the higher parts of these islands ; 

 nor are there any strata or remains of strata now existing, 



Plate XIX. ftp. 2. t PI-e XIX. fig. 3. 



