Geological Society of London, 475 



fine gravel, containing streaks and layers of coal, wliicli varies in 

 ■form from fine dust to large lumps. The fine gravel appears to be 

 entirely made up of local micaceous Silurian grit. 



The glacial strise run in a W.S.W. direction, and at first led the 

 author to infer that the coal had been drifted from that quarter. 

 This, however, would have involved the supposition that a portion of 

 the Coal-formation in situ liad been faulted down on the top of the 

 remarkable outlier of Mountain Limestone, which occurs about a 

 mile and a half west of Corwen. The author is therefore now of 

 the opinion that the coal was drifted from the Kuabon district during 

 a comparatively temperate interglaeial period. The land not being 

 submerged beyond a few hundred feet, it was floated along the sinu- 

 osities of the valley of the Dee, and stranded in the shallow water of 

 the Corwen area. Hence the transportation of debris may at times 

 have taken place in a direction diametrically opposite to that of the 

 glaciation of a district. 



23. •'' The Cephalopoda-beds of Gloucester, Dorset, and Somerset." 

 By J. Buckman, Esq., F.G.S. 



The author considers the Cephalopoda-beds of Bradford and 

 Dundry to be on the same horizon, and that neither the one nor the 

 other have the slightest connexion with the Cephalopoda-bed of 

 Gloucestershire. The Dorsetshire Cephalopoda-bed is the equivalent 

 of the *' Gryphite Grit " at Leckhampton, and the overlying roughly 

 bedded stone is the representative of the " Trigonia Grit " of Gold 

 Comfort. The Gloucestershire Cephalopoda-bed lies at the base of 

 the Inferior Oolite, whilst the Dorsetshire bed is at the top of that 

 formation. 



Part of the sands at Bradford Abbas really represent the lower 

 Oolitic mass of Leckhampton and Crickley ; in fact the Dorset sands 

 represent the lower freestones of Gloucestershire. The beds under- 

 lying the Dorsetshire Cephalopoda-bed are the equivalents of the 

 Inferior Oolite of Ham Hill. 



The author gives lists of the fossils from the freestone of Ham 

 Hill, and of the Cephalopoda from the Dorset equivalent of the 

 '' Gryphite Grit." The latter do not appear in zones, but different 

 species are prevalent at different localities, all on the same horizon. 

 The other fossils from this bed point to the same conclusions, as the 

 Ammonites are numerous and in good preservation. 



24. "Evidence of the Subsidence of the Island of Guernsey." 

 By E. A. Peacock, Esq., C.E., F.G.S. 



A].l round the coast of this island, like that of Jersey, are found 

 tree-trunks and other vestiges of old forest-land now submerged. 

 Passages are quoted by the author from various old historians relative 

 to the former existence of this tract of dry land, the submergence 

 of which probably took place in the fifteenth century. The encroach- 

 ment of the waters is due to the subsidence of the land, and not, as 

 has been suggested, to the breaking in of the sea through, some 

 natural barrier upon some already low-lying district. Judging from 

 the old chart of 1406, the amount of depression is equal to 160 feet. 



