Capt. Vetch on Terraces in the Isle of Jura. 417 



of clay with some sand and angular pebbles of quartz. This bed when it 

 reaches the sea is often undermined^ and the line of terrace upon it conse- 

 quently interrupted. Similar interruptions are sometimes occasioned by moun- 

 tain torrents ; and scanty as the vegetation is^ it is still sufficient to render the 

 continuity of the terraces in some places indistinct. On the surface of the 

 terraces,, situate (as I have said) sometimes on bare rock^ sometimes on alluvium, 

 we find a beach of round, smooth, white blocks of quartz as large as cocoa- 

 nuts. These are common to all the terraces, and identical in their appearance 

 with those which constitute on this side of the island the present beach of the 

 Atlantic. 



The width of the terraces, and the flatness of their surface, preclude the idea 

 that they were formed by a sudden and violent inundation, or in any other way 

 than by the action of tides and waves similar to those of the present sea. That 

 such was their origin, is further confirmed by a series of caves which occur at 

 one and the same level along a cliff on the north side of Loch Tarbert, some 

 hundred yards inland, and at a considerable height above the level of the sea. 

 Every other cave which I have seen in the quartz rock at Isla, Jura and Fair 

 Island, is situate on the shore, and has or may have been produced by the ac- 

 tion of the waves upon the cliffs : — those which are similarly distributed must 

 be ascribed to a similar cause. 



These phaenomena do not appear to extend beyond the limits I have assigned 

 to them. They are not seen on the east coast of Isla, nor in any of the adjacent 

 islands. The alluvium at Bornou in Isla, upon which Dr. M'Culloch has 

 reasoned, I think correctly, presents nothing analogous to the beaches I have 

 been describing : — in regard to that of Kyle haven in the Isle of Skye, I am 

 unable to speak with equal confidence. 



If, then, the terraces now appearing at different heights above the sea have 

 been each in its turn on a level with it, we can only account for their present 

 position by assuming several successive subsidences of the sea, or as many 

 successive risings of the land ; but the effect of the former would have been felt 

 all over the globe : the very limited area, therefore, over which these phae- 

 nomena can be traced, necessarily inclined us to embrace the latter hypo- 

 thesis. 



3h2 



