110 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [Dec. 8,
at that time. Later than this, considerably, however, and when far
larger tracts had become established as land, we get from the
Hessle clay evidence that ice adequate to the transport of blocks of
2 or 3 cubic feet in dimensions was in existence, though such
blocks are but very rare in it.
Discussion.
Mr. Gwyn Jeffreys had found the shells of Kelsea and elsewhere in Yorkshire to be mainly arctic, and Mr. Prestwich, in his paper on the Boulder-clay near Hull, had first pointed out their glacial character. In the late dredgings in H.M.S. 'Porcupine' several of the species before known as fossil at Bridlington, but not as existing in the British seas, had been discovered. In fact he believed that the Bridlington species, with but few exceptions, had now been found in the British seas. Similar species had also been found in the Boulder-clay in Scotland.
Prof. Ramsay was pleased to find the author's views so closely correspond with his own published some years ago as to the glacial phenomena of North Wales, though based on another part of the country. He thought that shells might be found by careful search in the low-lying Boulder-clay in other places than those enumerated, as they had been discovered in the western part of England.
Mr. Prestwich, though inclined to accept the divisions of the Boulder-clay in Yorkshire as suggested by the author, was not so clear as to his divisions in the south. He thought the presence of chalk in the clay might be traced to the contiguity of the outcrop of the chalk stratum. The shells being to a very great extent recent, the grouping might be due to accidental or local circumstances. The Chillesford clays, in his opinion, marked the commencement of the great Glacial period.
Mr. Etheridge suggested that Nucula Cobboldioe, Cardita similis, and some other shells not found in the British seas, proved the arctic character of the Bridlington fauna.
Sir Charles Lyell remarked that if the fauna of the Lower and Middle Glacial really corresponded so closely with that of the Crag, it afforded a strong argument against their being of the same age as the Bridlington beds. Perhaps eventually some palaeontological connexion might be traced throughout the series, and a chronological scale established.
The President suggested a difficulty in the marine transport of ice from Shap Fell to Bridlington, not only from the wind blowing rarely in the necessary direction, but from the current caused by the great submerged ridge also tending to carry any bergs in another direction. He thought the transport by sheet-ice more probable.
The Rev. J. L. Rome had traced the Shap granites over the valley of the Eden, across Stainmoor to the Yorkshire side. There might have been difficulties in their transport, but there they are. Though they were found in Teesdale, yet the intervening ridge of millstone-grit, 2000 feet, had prevented their finding their way into Swale Dale.
