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Marine Shells in Scotch Glacial Drift. Their Arctic Character. Rarity of Organic Remains in Glacial Deposits. Contorted Strata in Drift. Glaciation of Wales, England, and Ireland. Marine Shells of Moel Tryfaen. Erratics near Chichester. Glacial Formations of North America. Many Species of Testacea and Quadrupeds survived the Glacial Cold.
The old story of the raised beach on Moel Tryfaen is trotted out; though, even if the facts are as yet rightly interpreted, there is not a shadow of evidence that the change of sea-level in that locality was sudden, or that glacial Welshmen would have known it was taking place.
Trimmer had previously, in 1831, detected the signs of a great submergence in Wales in the Post-pliocene period. He had observed stratified drift, from which he obtained about a dozen species of marine shells, near the summit of Moel Tryfaen, a hill 1400 feet high, on the south side of the Menai Straits.
Even a Welsh antiquary might hesitate over the supposition that a tradition of the fate of Moel Tryfaen, in the glacial epoch, had furnished the basis of fact for a legend which arose among people whose own experience abundantly supplied them with the needful precedents.
The evidence of the marine origin of the highest drift is no doubt inconclusive in the absence of shells, so great is the resemblance of the gravel and sand of a sea beach and of a river's bed, when organic remains are wanting; but, on the other hand, when we consider the general rarity of shells in drift which we know to be of marine origin, we can not suppose that, in the shelly sands of Moel Tryfaen, we have hit upon the exact uppermost limit of marine deposition, or, in other words, a precise measure of the submergence of the land beneath the sea since the glacial period.
The height reached by these fossil shells on Moel Tryfaen is no less than 1300 feet a most important fact when we consider how very few instances we have on record beyond the limits of Wales, whether in Europe or North America, of marine shells having been found in glacial drift at half the height above indicated.
A marine molluscous fauna, however, agreeing in character with that of Moel Tryfaen, and comprising as many species, has been found in drift at Macclesfield and other places in central England, sometimes reaching an elevation of 1200 feet.
Thus, in the immediate vicinity of the vast expanse of country which can be proved to have been untouched by any catastrophe before, during, and since the "glacial epoch," lie the great areas of the AEgean and the Red Sea, in which, during or since the glacial epoch, changes of the relative positions of land and sea have taken place, in comparison with which the submergence of Moel Tryfaen, with all Wales and Scotland to boot, does not come to much.
Professor Ramsay estimated the probable amount of submergence during some part of the glacial period at about 2300 feet; for he was unable to distinguish the superficial sands and gravel which reached that high elevation from the drift which, at Moel Tryfaen and at lower points, contains shells of living species.
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