17o PROCEEDINGS OF THE GEOLOGICAL SOCIETY. 



(places respectively north-east and south-west of Lincoln) ; but it 

 seems to us to be of recent origin, and unconnected with the beds of 

 the denudation -series. 



Respecting the later Postglacial or scarp-augmenting part of the 

 denudation which has operated on the Lincolnshire area north of Cas- 

 tor, we would refer again to the sections, figs. 7 & 8, at page 402 of the 

 paper of the first-named of us, in the 23rd volume of this Journal. 

 These cross the great troughs within which, after the crests of the 

 chalk country of Hertfordshire and Cambridgeshire had emerged 

 and undergone denudation (much in the same way as the Wold- 

 crest has), the Postglacial sea had become confined, and wherein 

 it eroded the chalk along which it swept. A comparison of 

 these two sections with fig. 6 of our paper shows, we think, 

 that if, instead of receding from mid-Lincolnshire after it had 

 formed the valleys of that part by its earlier denudation, this 

 sea had continued to erode so as to sweep out the Glacial clay and 

 subjacent beds which are included within the broken hne of our 

 section, a section similar to that of fig. 8, in the 23rd volume, would 

 have resulted. Further, if this erosion, instead of acting precisely 

 thus, and forming a trough of which one side was chalk and the 

 other Glacial clay, as in the last-mentioned section, had swept away 

 the whole body of the Glacial clay lying between the eastern slope 

 of the Oohtic ridge (or " cliff") and the Wold, we should get exactly 

 the features displayed by Lincolnshire north of Castor, and illus- 

 trated by part of our section, fig. 5. Now, ivherever this has taken 

 place, there the continuous scarp of the chalk Wold extends; hut 

 wherever it has not, there tJie chalk is not thus scarped, but runs out 

 into those ridges formed of Chalk, Subcretaceous beds, and Glacial clay 

 together, or of the latter alone, both parallel with, and transverse 

 to the Wold-strike, or forms one of the sides of the Steeping trough 

 described in the previous part of this paper, and illustrated by figs. 

 6, 7, 8, 9, 10, and 11. If the Ordnance map be examined it will be 

 seen that these features begin a little south of Castor, and so continue 

 southwards to the Fen-border. It therefore appears to us that, just 

 to Castor, and no further, reached the tongue of the later Postglacial 

 sea which first swept out the Glacial clay, and subsequently, after the 

 interval gi\nng rise to the Hessle-clay deposit, swept out that clay 

 also along the west of the Wolds. 



Precisely similar features of denudation to those presented by the 

 western Wold-foot are, with the exception of the existence of these 

 denudation-sands, exhibited by the trough that runs along the north 

 Wold-foot as far as Hunmanby. At this place a narrow belt of purple 

 clay skirting the sea still fills the head of the trough, as shown at 

 the extremity of fig. 1, completely barring it in from the area oc- 

 cupied by the present sea ; so that the Hertford (an affluent of the 

 Derwent, which flows away from the sea westward along this trough 

 to Malton, and thence southward through the great depression into 

 the Humber) is fed by brooks taking their rise close to the sea in 

 this belt *. We have thus in this part the same barrier to the fur- 

 * See the part marked f in fig. 1. 



