474 Geological Society. 



layer of basalt has entirely disappeared. These intercalated (not 

 tnterstratified) beds of volcanic rock are common throughout the 

 district, and tend to prove the irruptivo nature of the Whin Sill, as 

 maintained by the late Prof. Sedgwick. 



21. « The Distribution of Flint in the Chalk of Yorkshire." By 

 J. R. Mortimer, Esq. 



The author considers that the present shape of the Chalk "Wolds of 

 Yorkshire seems to suggest that they are the remains of an atoll or 

 circular reef, probably one of a chain, rather than the fragment of a 

 vast sheet of Cretaceous mud deposited in deep water. He thinks 

 that the flint-bearing and non-flint-bearing chalk areas are in the 

 main contemporaneous in Yorkshire. The chalk without flint con- 

 tains 4-28 per cent, of silica, whilst the chalk with flint contains only 

 2-12 per cent. 



22. " On the Mode of Occurrence and Derivation of Beds of 

 Drifted Coal near Corwen, North Wales." By D. Mackintosh, Esq., 

 E.G.S. 



Besting on the lowest drift, which here, at an elevation of 

 500-600 feet above the level of the sea, consists of yellowish clay 

 alternating with beds of coarse gravel, is a deposit of clean sand and 

 fine gravel, containing streaks and layers of coal, which 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 striae 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 had 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 Ruahon district during a 

 comparatively temperate interglacial 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., E.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 Cold 

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

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

 formation. 



