Trap-Dykes--"Cotton Apples"--Alternation of Lacustrine with Marine Remains--Analogy from the Beds of Esk--Aspect of the Island on its narrow Front--The Puffin--Ru-Stoir--Development of Old Red Sandstone--Striking Columnar character of Ru-Stoir--Discovery of Reptilian Remains--John Stewart's wonder at the Bones in the Stones--Description of the Bones--"Dragons, Gorgons, and Chimeras"--Exploration and Discovery pursued--The Midway Shieling--A Celtic Welcome--Return of the Yacht--"Array of Fossils new to Scotch Geology"--A Geologist's Toast--Hoffman and his Fossil. We leave behind us the musical sand, and reach the point of the promontory which forms the northern extremity of the Bay of Laig. Wherever the beach has been swept bare, we see it floored with trap-dykes worn down to the level, but in most places accumulations of huge blocks of various composition cover it up, concealing the nature of the rock beneath. The long semi-circular wall of precipice which, sweeping inwards at the bottom of the bay, leaves to the inhabitants between its base and the beach their fertile meniscus of land, here abuts upon the coast. We see its dark forehead many hundred feet overhead, and the grassy platform beneath, now narrowed to a mere talus, sweeping upwards to its base from the shore,--steep, broken, lined thick with horizontal pathways, mottled over with ponderous masses of rock. Among the blocks that load the beach, and render our onward progress difficult and laborious, we detect occasional fragments of an amygdaloidal basalt, charged with a white zeolite, consisting of crystals so extremely slender that the balls, with their light fibrous contents, remind us of cotton apples divested of the seeds. There occur, though more rarely, masses of a hard white sandstone, abounding in vegetable impressions, which, from their sculptured markings, recalled to memory the Sigillaria of the Coal Measures. Here 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 fragmentary 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 building, 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 protrusions and land-slips, we find some difficulty in tracing their order of succession.