GENERAL COMPARISON, &C. 497 



GENERAL COMPARISON OF THE CLYDE ISLANDS. 



IN the former comparisons which have been drawn 

 between the several members of the different groups into 

 which the Western islands were distributed, it must have 

 appeared that these associations were founded, rather on a 

 mutual resemblance of character than on a common geo- 

 graphical bond. In the present instance, the general com- 

 munity of structure must be considered as pervading the 

 whole conjointly ; being only rendered discernible by 

 viewing the several islands as parts of one great division, 

 the several portions of which are, in a geological sense, 

 mutually dependent on each other, although geographically 

 discontinuous. The surrounding shores of the mainland 

 present the same general structure ; the several corre- 

 spondences occurring on one part or another of the 

 great aestuary of the Clyde in which these islands are 

 embayed. Thus the present group becomes intimately 

 connected with the adjoining continent; and, while the 

 history of the several islands explains the relations and cha- 

 racters of the different strata on that shore, the more ex- 

 tensive continuity of the latter serves to restore to the 

 islands that mutual dependence which is rendered less ap- 

 parent in consequence of their disjunction. The geo- 

 graphical bond by which these islands are here united, 

 is thus proved to be also a geological one ; although at 

 first less obvious than in the preceding cases where, on 

 a general view, it appeared to be more intimate. 



The general structure of that part of the mainland which 

 corresponds to the islands of the Clyde, has already been 

 mentioned in describing the schist of Bute. From that 

 description it appears that the primary district of the 

 Highlands is immediately followed by an extensive tract 

 of red sandstone ; the prolonged mutual boundary of 

 . VOL. ii. K K 



