158 PEOCEEDIN^GS OP THE GEOLOGICAL SOCIETT. 



pression lias been so unequal that while the gravels of that series 

 under Grimsby descend to 100 feet below high water, they gradually 

 rise in going northwards towards Bridlington, so that their bases, 

 as shown in fig. 1, are considerably above the beach near that 

 place*. "We learn also from Mr. Ball, of Brigg, and from Mr. Atkin- 

 son, the engineer of the Ancholme navigation, that the remains of a 

 forest which was composed principally of yew and oak exist beneath 

 the marshes of the Ancholme, at a depth of 13 feet below high water 

 of ordinary spring tide in the Humber estuary. This forest is capped 

 by 6 feet of clay, with the-remains of freshwater plants, upon wHch 

 is another and similar forest-bed ; from which it would appear that 

 the depression which has so greatly afiPected the coast twenty miles 

 to the east of the Ancholme has, but in a less degree, also affected 

 the parts inland, so as to bring the site of a forest which had grown 

 in the trough lying on the west of the north Lincolnshire "Wold, 

 subsequently to its desertion by the waters of the Hessle-clay sea, 

 once more below the sea-level, and caused it to be overspread with 

 the deposit of the fresh waters of the Ancholme. 'We have also 

 reason to believe that evidences of this recent easterly depression of 

 a late Postglacial forest-suiface, varied by some slight oscillations, 

 obtaiu further south over the area of the great fen country. The 

 same evidences of a late depression appear to exist along the edges of 

 the Severn Estuary, on the Lancashire, and on some parts of the 

 southern coast, but not, we think, to so great a depth as at Grimsby. 

 Is'evertheless, although these evidences of recent depression occur on 

 both sides of England, their general absence suggests that this de- 

 pression has not been uniform. 



In considering the direction in which the purple clay has been 

 denuded, and the action which has brought the scarp of the York- 

 shire and north Lincolnshire Wold into the condition we see it now, 

 we have, as we propose further on to show, been led to the conclu- 

 sion that the Postglacial sea, previously to the formation of the 

 Hessle clay and gravel, had its place on the west of the Wolds, all 

 to the east of them being land, and that the same thing was re- 

 peated after the elevation of the Hessle clay. The excavation, 

 therefore, of the troughs containing the series / through the Hessle 

 clay, the relation which they appear to have with the sea in its 

 present place, the formation and subsequent burying of these blow- 

 well channels, coupled with the depression of the land surface at 

 Hull and Grimsby at some period subsequent to the Hessle clay (on 

 which the forest rests at Hull), appear to us to have a manifest 

 connexion with that very recent easterly depression, followed by 

 partial and unequal elevation, which the first-named of us has 

 traced as having affected the country round the Thames mouth f, 

 and which seems to be traceable also in the silting up of the river- 

 valleys of north-east Xorfolk, to which the Eev. J". Gunn has called 



* It is impossible to suppose this inequaHty to be due to the wearing back of 

 the cliff, as these gravels are highest where the chff yields least, namely north 

 of Bridhngton. 



t Quart. Journ. Geol. Soc. toI. xxiii. p. 414. 



