Page:Quarterly Journal of the Geological Society of London, vol. 33.djvu/178

140 140 F. W. HARMER OX THE KESSLNGLAND CLLFF-SECTIOX.

Crag contains, similarly, Crag -shells*. The occurrence in it of marine mollusca is hardly to be reconciled with the theory that the stone- bed represents a terrestrial surfacef.

Discussion.

Mr. Charles worth, referring to Mr. Whitaker' s paper, stated that he regarded the non-fossiliferous sands as Crag. At Felixstow the London Clay is under the Crag, and without fossils ; hence he argued that the fossils were not removed by chemical means, but that they never were there. He could not believe that sharks' teeth would be dissolved away by water charged with carbonic acid ; but he had never seen sharks' teeth in the sands. With regard to Mr. Harmers paper, he said that the mammalian remains in the subangular beds must of necessity be rounded, but that they are not therefore necessarily derivative. The Crag must have had a land- fauna, the remains of which would be carried down streams by floods, as in Australia. If the fossils are derivative, he asked, Whence are they derived?

Prof. Hughes, in confirmation of the view advocated by Mr. Whitaker, mentioned cases which had come under his observation in the Faluns and in the chalky gravel of Cambridge, where the removal of the carbonate of lime from the upper part by percolating acidulated water produced phenomena similar to those described by Mr. Whitaker. He pointed out that other peculiarities, such as the vertical arrangement of the pebbles dropped into the pipy hollows, the looping of the earthy residuum, the frequent coincidence of the pipes and pans with surface-features, and various other conditions affecting the collecting and passage of the acidulated water, proved that the explanation offered was the true one.

Prof. Seeley maintained that the irregularities of the gravels described by Mr. Whitaker were due to staining by iron and solution by carbonic acid, liberated by the growth and decay of vegetation and old forests. He thought that they only differed from the forest stainings which cap most Postglacial gravels in being of greater thickness. The fact of interglacial denudation as described by Messrs. Wood and Harmer seemed to him self-evident from the elevation of land after the Middle Glacial beds were deposited.

Prof. Morris remarked that the whole subject was one of extreme difficulty. He thought that the occurrence of mammalian remains at the base of each of the Crags needs further investigation. The interglacial formation of Switzerland represents the forest-beds of Norfolk.

Prof. Hamsay said that there was a growing opinion that the

Publications for 1874, p. 151.
 * For one instance of this see Supplement to 'Crag Mollusca ' in Pal. Soc.

f Mr. 8. Woodward, in his ' Geology of Norfolk ' (1823), taking the same view of this stone-bed, points out that a precisely similar deposit is now form- ing on the Cromer coast in places where the bed of the sea is composed of chalk.