450 On Siafa. 



Sky. The whole isl^tiid of Mull, with the exception of the Rossy 

 is of a trap forniaticni, coiitaiiiing however some partial tracts of 

 sat'.dstone and otlier rocks which I nedd not notice. The islands 

 of Ulva and the Treshanish, with their dependent rocks, are 

 also of trap formation. So are the islands which lie to the 

 north, and which 1 have enumerated aljove. lona hov.ever, to- 

 gether with Coll and Tirev, consists priiicipally of gneiss and 

 mica slate traversed by granite veins, rocks which also form the 

 chief parts of the coasts of Lorn, Appin, Morven, and Ardiia- 

 murchan. 



It is to the former, then, that we must look for the origin of 

 the rolled stones which cover Staffa, if, limiting the great 

 operations of nature by our own narrow views, and the ages 

 which have contributed to change the face of the globe by our 

 ov.n sliort span, we are led to seek for that solution which may 

 appear the least difficult. Even then, we must admit that Stafta 

 has formed part of one continuous land with the islands of Coll, 

 Tirey, and Mull, since no transportation could have been effected 

 without the existence at some period of a continuous declivity 

 between them. 



The language whicli this circumstance speaks is not obscure, 

 and the nature of these changes allows of little dispute. If we 

 admit this ol)litcration of so large a portion of solid land, and 

 consider th-at a deep sea now rolls above the foundations of for- 

 mer mountains, we have no further difficulties to obstruct us in 

 accounting for the numerous and distant accunmlations of trans- 

 yiorted materials which occur over the Avhole surface of the 

 earth. The same power, whatever it was, that hollowed the 

 great sinuosity of Mull, might well remove the solid matter that 

 once filled the valleys whicli now separate Mont Blanc from the 

 ridge of Jura. 



But if, appallefl at the supposed magnitude of those changes, 

 and at the period of time which must have elapsed to complete 

 them, we suppose that the island of Staffa was elevated from 

 the bottom of the sea in its present detached form, and retaining 

 On its suunnit a portion of the bed of loose matter deposited 

 under the ))resent waters, another order of phaenomena crowds 

 on us no less important, and involving circumstances almost 

 equally repugnant to the visible operations of nature. 



The appearances are perhaps insufficient to enable us to de- 

 cide between two difficulties of ecjual magnitude, nor is it here 

 necessary to enter further on that question. I may also leave 

 it to those who have engaged more deeply in such investigations, 

 to determine whether, in the supposition of the first of these 

 causes, whether the wasting of the land has arisen from the gra- 

 dual action of natural operations, or the more violent efforts of an 



occasional 



