242 RASAY. GEOLOGV. 



to form a second ridge below them ; while, in other 

 places, huge piles of ruin cover their slopes with frag- 

 ments, advancing far into the sea and strewing the shore 

 with rocks. None of the islands, not even Sky itself, 

 illustrates so strongly the magnitude of the changes that 

 take place from the operation of daily causes ; changes 

 however, which, although more palpable, are not perhaps 

 more effectual than those which occur in many situations 

 where they do not carry so strong and permanent a record 

 with them. 



Excepting these, there are few marks of waste in the 

 island; as it gives rise to no rivers worthy of notice, 

 and the mountain rains, reaching the sea soon after 

 they have quitted the clouds by courses the most easy and 

 direct, leave few traces of their ravages. At its southern 

 extremity is found an alluvium of rolled stones, forming 

 a sea bank of an origin which is not apparent; since it 

 is not connected with any river, and is far too high to 

 have been thrown up by the tides. A similar one, but 

 of smaller extent, is found near Clachan. These are, 

 possibly, the remains of some more extensive deposit of 

 a diluvian nature ; a circumstance rarely occurring in the 

 Western islands, but of which another example still more 

 remarkable will hereafter be pointed out in Sky. 



IN describing the geological structure of Rasay* I shall 

 commence with the gneiss ; since by means of this rock 

 it is connected with Rona, and since this is also the lowest 

 substance in the island. It occupies the whole of the 

 northern extremity, and is defined at its southern boun- 

 dary by a line drawn from Brochel Castle in a N. by W. 

 direction, passing through the Lake of the Reeds and 

 crossing the narrow sound which separates Rasay from 

 Flodda. This boundary is not however rectilinear, as the 

 gneiss occasionally intrudes within that space, which, on 



* PI. XIII. fig. 4, 5. 



