INTRODUCTORY REMARKS, &C. 309 



INTRODUCTORY REMARKS ON THE CLYDE ISLANDS. 



THE last division of the Western islands consists of 

 those that are embayed in the great estuary of the Clyde. 

 These, on a first view, appear rather to be associated by a 

 geographical bond than by any extensive traces of geolo- 

 gical affinity. Yet in this respect also it will be found 

 that they present many important resemblances ; being so 

 related to each other in certain essential circumstances, 

 that the description of one can scarcely be rendered 

 thoroughly intelligible without having recourse to the 

 rest. Even where the structure of any one of them 

 requires no aid from a consideration of others, the general 

 interest of the appearances is materially increased by a 

 collective examination and comparison of the whole. 



Arran indeed may in one sense be considered as an 

 independent object; displaying a greater extent and a 

 more perfect series of geological arrangement than any 

 of the Western isles ; and capable, to a great degree, of 

 elucidation from its own internal stores. Yet even this 

 island presents irregularities, if not difficulties, which can 

 scarcely be explained, or placed in a satisfactory light, 

 without resorting to the illustration that may be derived 

 from the remaining islands and the adjoining continent. 



Although the granite of Arran must be considered a soli- 

 tary feature, that island possesses a common relation with 

 Bute and Inchmarnoch, in the primary schists which are 

 found in the whole ; while one of its most interesting con- 

 nexions with the mainland also, will be hereafter seen to con- 

 sist in these rocks ; which possess a very extensive commu- 

 nity of character and position through a large part of the 

 continent of Scotland. The red sandstone, with scarcely an 

 exception, pervades the whole group ; and under a very 



