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Show 72 NEWint PLIOCENE PERIOD. [Ch. VI, No.9. Soutllside ofpa&&, No.IO. Section of tlte same beds on tlte no1·tll side of tlte pas&. The disposition of the strata, on both sides of the pass, is most singular, and remarkably well exposed, as the harder layers have resisted the weathering of the atmosphere and project in relief. The sections exhibited on both sides of the pass are nearly vertical, and do not exactly correspond, as will be seen in the annexed diagrams (Nos. 9 and 10). It is somewhat difficult to conceive in what manner this arrangement of the layers was occasioned, but we may, perhaps, suppose it to have arisen from the throwing down of calcareous sand and volcanic matter, upon steep slanting banks at the bottom of the sea, in which case they might have accumulated at various angles of between thirty and fifty degrees, as may be frequently seen in the sections of volcanic cones in Ischia and elsewhere. The denuding power of the waves may, then, have cut off the upper Ch. VI.] SJCILY-VAL DI NOTO. 73 portion of these banks, so that nearly horizontal layers may have been superimposed unconformably, after which another bank may have been formed in a similar manner to the first. Volcanic conglomerates.-In the Val di Noto we sometimes meet with conglomerates entirely composed of volcanic pebbles. They usual1y occur in the neighbourhood of masses of lava, and may, perhaps, have been the shingle produced by the wasting cliffs of small islands in a volcanic archipelago. The formation of similar beds of volcanic pebbles may now be seen in progress on the beach north of Catania, where the waves are undermining one of the modern lavas of Etna; and the same may also be seen on the shores of Ischia. Proofs of gradual accumulation.-In one part of the great limestone formation near Lentini, I found some imbedded volcanic pebbles, covered with full-grown serpulre, supplying a beautiful proof of a considerable interval of time having elapsed between the rounding of these pebbles and their inclosure in a solid stratum. I also observed, not far from Vizzini, a very striking illustration of the length of the intervals which occasionally separated the flows of distinct lava-currents. A bed of oysters, perfectly identifiable with our common eatable species, no Jess than twenty feet in thickness, is there seen resting upon a current of basaltic lava; upon the oyster-bed again is superimposed a second mass of lava, together with tuff' or peperino. Near Galieri, not far from the same locality, a horizontal bed, about a foot and a half in thickness, composed entirely of a common Mediterranean coral ( Caryophyllia cespitosa, Lam.), is also seen in the midst of the same series of alternatinO' . d 0 1gneous an aqueous formations. These corals stand erect as t~ey grew, anc.l after being traced for hundreds of yards, are agam found at a corresponding height on the opposite side of the va1ley. Dip and di·rection.- The disturbance which the newer Pliocene strata have undergone in Sicily, subsequent to th · d · · d'ffi eJr epos1t10n, 1 ers greatly in different places; in general, however, the beds are nearly horizontal, and are not often |