STAFFA. GEOLOGY. 21 



stratum towards the western side, which it intersects 

 in a vertical direction ; and having yielded, as is ge- 

 nerally the case, to the action of the sea, it has left 

 a large fissure. A second may be observed intersecting 

 the lateral and western wall of Mackinnon's cave, and 

 a third is seen among the large columns on the eastern 

 side of the cave of Fingal; running among them in a 

 parallel course so as not to be readily distinguished. 



But I must not quit Staffa without describing a bed 

 of matter which, however foreign to the structure of the 

 island, is by no means foreign to its mineral history ; 

 giving rise, at the same time, to geological questions 

 of considerable importance. This is an alluvial deposit 

 consisting of various transported stones, which may be 

 seen on the surface in different parts of the island. 

 It is particularly conspicuous near the landing-place, 

 and on the western abrupt edge of the cliff. The 

 fragments are of various kinds, consisting of quartz, 

 granite, and blue schist, intermixed with blue quartz 

 rock, and trap; all of them being substances which 

 enter into the composition of the neighbouring islands 

 of Rum, Sky, and Mull, but which are found in situ 

 no nearer than in the latter island. I have on different 

 occasions throughout this survey remarked how rarely 

 foreign alluvial matter occurs in the Western islands. 

 It is here therefore the more remarkable; while the 

 distance of Staffa from the neighbouring shores of Mull, 

 which is not less than seven miles, adds not a little 

 to the interest attending it. The surface of the earth 

 every where presents appearances indicating great changes 

 and revolutions ; of which none are perhaps more un- 

 questionable than the existence of transported stones 

 and alluvial substances in countries far removed from 

 those where similar rocks are now found in their natural 

 situations. These are familiar to geologists, and have 

 been subjects of much discussion. The insular position 

 of the example now under consideration, is sufficient 

 to prove that it could not have resulted from the flow 



