A SUMMER RAMBLE AMONG THE HEBRIDES. 69 



and there, too, we find fragments of a calcareous stone, so 

 largely charged with compressed shells, chiefly bivalves, that 

 it may be regarded as a shell breccia. There occur, besides, 

 slabs of fibrous limestone, exactly resembling the limestone 

 of the ichthyolite beds of the Lower Old Red ; and blocks 

 of a hard gray stone, of silky lustre in the fresh fracture, 

 thickly speckled with carbonaceous markings. These frag- 

 mentary masses, all of them, at least, except the fibrous 

 limestone, which occurs in mere plank-like bands, represent 

 distinct beds, of which this part of the island is composed, 

 and which present their edges, like courses of ashlar in a build- 

 ing, in the splendid section that stretches from the tall brow 

 of the precipice to the beach ; though in the slopes of the 

 talus, where the lower beds appear in but occasional protru- 

 sions and landslips, we find some difficulty in tracing their 

 order of succession. 



Near the base of the slope, where the soil has been under- 

 mined and the rock laid bare by the waves, there occur beds 

 of a bituminous black shale, resembling the dark shales so 

 common in the Coal Measures, that seem to be of fresh- 

 water or estuary origin. Their fossils, though numerous, are 

 ill preserved ; but we detect in them scales and plates of fishes, 

 at least two species of minute bivalves, one of which verv 

 much resembles a Cyclas ; and in some of the fragments, shells 

 of Cypris lie embedded in considerable abundance. After 

 all that has been said and written by way of accounting for 

 those alternations of lacustrine with marine remains which 

 are of such frequent occurrence in the various formations, 

 secondary and tertiary, from the Coal Measures downwards, 

 it does seem strange enough that the estuary, or fresh-water 

 lake, should so often in the old geologic periods have changed 

 places with the sea. It is comparatively easy to conceive 

 that the inner Hebrides should have once existed as a broad 

 ocean-sound, bounded on one or either side by Oolitic islands, 



