150 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. 



in the midst of the most boulder-bearing horizon of the purple clay 

 most satisfactorily harmonizes with the character of the shells them- 

 selves, which, as the late Dr. Woodward observed *, indicate the for- 

 mation yielding them to have been accumulated " during the climax 

 of the last gTeat age of cold in Britain ;" while position and organic 

 contents appear alike to indicate its deposit to belong to a stage in 

 the subsidence ushering in the purple clay that was prior to the 

 submergence of the higher parts of the Wold. In a word, it seems 

 to us to belong to the lower part of the purple clay, or that in which 

 there is a little chalk. 



Resting upon an extremely denuded surface of the purple clay, 

 and even in some cases upon the basement clay itself, where the 

 denudation, following upon the elevation of the purple clay, has cut 

 through the latter, occur the beds marked d and e. As both of 

 these are well developed in the generally known section at Hessle, 

 on the Humber, where they rest directly on the chalk, they may be 

 appropriately termed the Hessle sand (or gravel) d, and the Hessle 

 (Boulder-) clay e. Both of these deposits appear to us to afford the 

 clearest indications of having been formed after the purple clay had 

 been denuded from all that area where the chalk is now exposed, 

 and of having been deposited on the denuded surfaces. Different 

 both in colour and in character from the purple clay, the Hessle 

 clay can generally be distinguished from it at a glance, being more 

 earthy, less tenacious, and its foxy red colour being variegated by 

 cinereous vertical partings. Its best characteristic, however, is the 

 presence in it of irregular-shaped fragments of chalk, not abundant, 

 but sufficiently so to make a marked contrast with the chaMess 

 upper portion of the purple clay on which it so frequently rests. 

 The Hessle gravel d has a considerable but not uniform develop- 

 ment under the clay e, being constantly overlapped by the latter f. 

 Its position, usually in the lower part of the troughs, indicates the 

 shoal conditions which introduced the resubmergence giving rise to 

 the Hessle clay ; and at Hessle quarry the sand-bed {d) is divided 

 from the brecciated surface of the chalk by a thin bed or pan of 

 indurated ripple-marked mud ; and at South Ferriby it is divided 

 from its superincumbent clay by a similar pan t- Generally along 



* Geol. Magazine, vol. i. p. 52. 



t This overlap may be adyantageously studied in the Hessle Eailway-cutting, 

 at which place both beds, having overlapped for some miles the denuded purple 

 clay, rest immediately on the chalk. 



X A short notice of the Hessle beds, by Prof. Phillips, as they occurred forty 

 years ago, having, since this paper was read, been before the Society, it is un- 

 necessary to refer here to the organic remains enumerated by him from the 

 Hessle gravel ; but we woidd take the opportunity of observing that our remarks 

 as to overlap and shoal conditions assume the contiguity of the shore, which 

 he considers these organic remains to indicate. That contiguity, however, is 

 equally consistent with the Postglacial age which we assign to this gravel, as 

 with the Prseglacial one for which Prof. Phillips still contends, because the 

 period to which we refer it is one when the area embraced in our paper had, 

 after the denudation of the Glacial clay from a large part of it, become land, and 

 one which was followed by the localized subsidence that gave rise to the Hessle 

 clay. Entertaining, as all must do, the highest respect for the opinion of Prof. 



