WOOD AND ROME — LINCOLNSHIRE AND S.E. YORKSHIRE. 153 



at Hull) anything like the basement clay intervening. From Clee- 

 thorpe the Hessle clay extends southwards over the belt of undu- 

 lating ground called " The Middle Marsh," which it envelopes, 

 overlapping the lower part of the eastern Wold-slope. It is well 

 shown around Alford, where the brick-pits afford good sections, and 

 where it is seen to be overlain by 4 or 5 feet of a light-brown silt, 

 which seems to be of recent origin, and not improbably identical 

 with that near Nocton and Langworth referred to post (p. 177). 

 Four miles south of Alford the Wolds terminate, and the East Lin- 

 colnshire marsh sweeps round to the mouth of the Steeping valley. 

 Fringing that marsh and forming a belt between it and the high 

 ground, the Hessle clay sweeps round also, and occupies (where 

 it opens on the marsh near Firsby) the mouth of the Steeping 

 valley, which, when describing the structure of central Lincoln- 

 shire, we shall endeavour to show is a valley formed out of the 

 Upper Glacial clay and Cretaceous beds together by that part of the 

 Postglacial denudation which was anterior to the deposition of the 

 Hessle clay. The southern extension of the Hessle clay beyond the 

 Steeping mouth, near the southern extremity of the Wold, is obscure, 

 owing to the flat nature of the country. 



The gravel of Kelsea Hill, the subject of the notice by Mr. Prest- 

 wich*, is (now that the ballast-pit has been more extensively 

 worked) shown most distinctly to be overlain by this Boulder- clay 

 of Hessle, no less than 15 feet of it being so exposed in one part f. 

 Whether this gravel rests upon the basement and purple clays, or 

 either of them, or whether it be the gravel pierced beneath the 

 basement clay in a boring at Sunk Island, elevated for two or three 

 miles round Kelsea Hill, there are no means at present of deter- 

 mining ; but we strongly incline to think that the Kelsea-Hill gravel 

 is only an unusually thick and fossiliferous development of the Hessle 

 gravel. It is certainly singular that, considering the frequent ex- 

 posures of the latter along the coast, none of the organic remains so 

 abundant at Kelsea Hill should occur in them. These exposures, 

 however, are generally too inaccessible to allow of a proper search 

 for organic remains to be made. The only gravel-beds on the coast 

 (except that at Paull on the Humber, which rests on the purple clay, 

 and seems identical, as Mr. Prestwich supposes, with the Kelsea de- 

 posit) in which we have been able to detect mollusca belong to the 



* Quart. Joum. G-eol. Soc. vol. xvii. p. 446. This Kelsea is near Hedon ; 

 there is a Kelsey in North Lincolnshire, five miles west of Castor, near which 

 another gravel occurs, belonging probably to the series described by us in the 

 latter part of this paper under the heading of denudation-beds. 



t It was a conviction of this inferiority of the Kelsea-Hill gravel to clay 

 then regarded as the ordinary Yorkshire Boulder-clay, and shown in the Hessle 

 section, that led the first-named of us to the opinion (expressed in 1864) that 

 this gravel belonged to the Middle Glacial formation. The subsequent discovery 

 by us that the clay of Hessle was of distinct age from the great Boulder- (or Upper 

 Grlacial) clay formation, with which it had hitherto been confounded, at once 

 negatived that opinion. It is the 20 feet of red clay full of stones, of the Old 

 Pollard-farm boring, regarded by Mr. Prestwich (vol. xvii. p. 455) as "repre- 

 senting the Boulder-clay," which seems to us to be the Hessle clay which so 

 clearly overlies the Kelsea gravel in the ballast-pit. 



