22 THE GEOLOGIST. 



for storing lumber. The rough blocks of granite have fallen from the 

 top of the entrance so as to form a rude arch, and imbedded in the rock 

 forming the sides of the entrance are to be seen several large round 



Lign. 2. — Natural Cave on the Hugh — a, a, Rounded Boulders of Grc.nite. 



boulders of granite, almost as regular as if they had been turned in 

 a lathe, and compactly fixed in the matrix of the rock. Now this 

 spot is considerably above the present level of the sea, probably from 

 150 to 180 feet, and the boulders of granite bear all the marks of 

 having been long rolled on a rough sea-beach. Moreover, I was 

 assured by the masons to whom I referred above, that they had been 

 engaged in repairing the guard-house floor; and on digging beneath it, 

 they found other boulders, of precisely the same character as those at 

 the sides of the cave, firmly imbedded in the soil. It is manifest, then, 

 that the spot now adjoining the guard-house must once have been on 

 a level with the surrounding sea, or, at any rate, at no great elevation 

 above it, for glacial action alone would be, I conceive, scarcely suf- 

 ficient to account for the presence of these rounded boulders, so deeply 

 impacted in the solid rock. 



It becomes interesting, therefore, to inquire whether there are 

 any traces of volcanic or subterranean action still visible in these 

 islands, to which this upheaving of the land, after one or, it 

 may have been, frequent submersions, may be attributed. And a 

 careful investigation will bring to light several proofs of such 

 volcanic or subterranean force. In the direction of the causeway,. 



