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Every rock-suriace on which it rests is grooved and striated ;almost every softer pebble which it incloses is scratchedand farrowed, usually in the line of its longer axis; all itslarger shells exist as broken fragments, often rounded as ifby attrition, and bearing in their lines and scratches marksof the same agents that dressed the rocks and scored thepebbles; nay, the very substance and colour of its prevail-ing clays show that it is mainly composed of the dressingsof the rocks on which it rests,—all giving evidence, appa-rently, of a time when our half-foundered country sat fromeight hundred to a thousand feet lower in the water than itdoes now, and vast packs of grinding icebergs went careeringover what are now its lower hills and its higher table-lands.
The Clyde beds and their contents belong apparently to astill later time. Their largest shells are usually in a stateof great entireness and fine keeping. I had the pleasure oflaying open, two years ago, at Fairlie , on the Ayrshire coast,a virgin deposit unknown before, in which I found conti-nuous scalps of Pecten Islandicus still occupying the place inwhich they had lived and died, and with their upper valvescovered with large balanse, such as we now dredge up fromthe outer limits of the laminarian zone, and all fresh and un-broken. Huge Panopoea were there sticking fast in an unc-tuous clay, with their open siphuncular ends turned upwards;and entire specimens of Cyprina Islandicus and Modiola Mo-diolus, with their valves still connected by the sorely decayedligament. Tellina proxima was abundant, but reduced insize to little more than half the Gamrie dimensions. I foundAstarteellipticathe prevailing Astarte ; and groupes of youngerCyprina huddled together in the character—which they donot now assume on our coasts—of gregarious shells. Hocrushing iceberg had passed over this deposit: a groovedand polished rock of Old Red Sandstone lies beneath, over,laid by a thin stratum of red clay, apparently derived from