480 Geological Society. 



sions and elevation that they indicate a pluvial period just as clearly 

 as the Northern Drift indicates a Glacial. This Pluvial period must 

 have immediately preceded the true Historical period. 



November 20, 1867.— Warington W. Smyth, Esq., M.A., F.R.S., 

 President, in the Chair. 



The following communications were read : — 



1. "On the Glacial and Postglacial Structure of Lincolnshire 

 and South-east Yorkshire." By S. V. Wood, Jun., Esq., F.G.S., 

 and the Rev. J. L. Rome, F.G.S. 



The features of Yorkshire and North-east Lincolnshire having 

 distinctive characters from those of Central and South Lincolnshire, 

 the authors described the two areas separately. In the former, their 

 coast sections exhibited the Glacial clay separated into two portions : 

 of these the lower, which they identified with the ordinary (or 

 upper) Glacial clay of the South, contains abundant chalk debris ; 

 but the upper or purple portion (which was in places divided from 

 the lower by sand and gravel beds) contains no chalk in the upper, 

 and but little in the lower part of it, the place of the chalk being 

 taken by swarms of Palaeozoic fragments. The latter of these clays 

 alone extends over the Wold-top at Speeton, and alone occupies 

 the valley along the northern Wold-foot, and so away northwards to 

 Scarborough and the Tees' mouth, from which the authors inferred 

 that the north of England did not subside beneath the glacial sea 

 until after the south had been submerged. The, so-called, Bridling- 

 ton " Crag " was shown to be an intercalated bed in this purple clay. 

 Both these clays were shown to be denuded, and their denuded 

 edges to be everywhere covered by a much thinner Boulder-clay, that 

 of Hessle, which wraps Holderness like a cloth, extending to alti- 

 tudes of 150 feet, and running down the east of Lincolnshire to the 

 Fen-border. This Postglacial Boulder-clay of Hessle is again cut 

 through, and in those places covered by posterior beds of gravel, 

 one of which (at Hornsea) contained fluviatile shells. At Hull this 

 clay supports a forest, which is now submerged 33 feet below the 

 Humber, the same submerged forest also occurring at Grimsby. 

 The authors regarded the position of the sea during the Postglacial 

 period as having been principally on the west of the Yorkshire and 

 North Linconshire Wold until the formation of the gravel- troughs, 

 cutting through the Hessle clay, and that its present position 

 was connected with a recent westerly elevation and easterly de- 

 pression. 



The Glacial clay of Central and South Lincolnshire belongs to the 

 chalky portion, from which all the superior or purple part of the 

 formation has been denuded ; and the valleys of Central Lincoln- 

 shire were shown to be cut out of the Cretaceous series and Glacial 

 clay as a common bed, the hills formed of the clay rising to eleva- 

 tions equal to the Wold in that part. 



The Glacial clay of both areas was shown to be denuded west- 

 wards, and the denuded edges occupied with sands and gravels, 

 termed by the authors denudation-beds. 



