88 



granite, a very few only of slate being found. They are scattered in 

 great numbers over every part of the island, and are often of enor- 

 mous magnitude. They are most abundant and largest in the 

 vicinity of the granite nucleus, as about Corrie and the shore at 

 Corrygills ; and generally less numerous, and of smaller bulk, in the 

 remote southern districts. Occasionally, however, some very large 

 ones occur even there. They are limited to no particular locality, 

 but occur alike in the valleys, on the summits and northern 

 and southern slopes of the hills, in situations to which they must 

 have passed across deep and narrow glens. They are found also iso- 

 lated on the Holy Isle, which is separated from the mainland by a 

 wide bay, and two deep navigable channels. Blocks of the coarse- 

 grained variety are much more numerous than those of the fine. 

 The latter, indeed, are in a great measure limited to the tracts on 

 which Glen lorsa, the principal seat of this variety, opens towards 

 the south ; and this fact, in connection with the more sparing distri- 

 bution of the blocks along the northern coast, on which but one 

 glen with a narrow opening debouches, than in other parts of the 

 island, shows that, though the dispersion has been quaquaversal, 

 it has been to a large extent determined by the direction of the 

 valleys. Dr. MacCulloch, who has noted the leading facts regarding 

 the dispersion of the granite blocks with great accuracy, though 

 imperfect in many of his details, closes his account with the following 

 observations : " None of the blocks have the marks of a distant 

 origin ; all have the characters of the granites of the adjoining moun- 

 tains, characters sufficiently distinct from those of almost all the 



granites of Scotland No situation, perhaps, has 



been pointed out where the origin of the travelled blocks is more 

 obvious, or their new position more difficult to comprehend, without 

 assuming considerable revolutions of the surface of the land over 



which they have passed The compact and 



solitary position of the fixed mass of granite, the identity of the 

 materials of this mass with that of the travelled stones, the gradual 

 diminution of these as they recede from the parent rock, and the 

 insulated position of the whole, render their origin indubitable, and 

 present to the geologist a spot, on the changes of which he may 

 speculate, with the certainty that he has before him a set of incon- 

 trovertible data from which to reason." (Ut sup., p. 341.) 



This passage places in a clear light the conditions of the problem, 

 and the difficulties attending it. The author does not, however, 

 propose a solution of the difficulties, nor does he enter into any theo- 

 retical discussion. His account of the travelled blocks is the only 



