176 PROCEEDIXGS OF THE GEOLOGICAL SOCIETY. 



as is possible, the equivalents of that clay due to the different phy- 

 sical conditions obtaining within this enclosed area. It is, however, 

 not unlikely that gravels of more than one Postglacial age are in- 

 cluded among the beds along this foot of the Wold. 



The beds west of the Wold-scarp (which are principally gravels 

 composed entirely of local materials) are developed at Cadney, 

 Wrawby, Barnetby, and Brigg*, in Lincoln shn-e, and at Brough 

 Cave, Hotham, and Market Weighton, in Yorkshire ; and they occupy 

 the valley below the western scarp in places where the Hessle clay 

 must (from its position in the Humber gorge, and at the consider- 

 able elevations just referred to) have once existed. As there 

 is no reason for supposing these to form any part of the Hessle gravel 

 (d), left exposed here by the removal of the Hessle clay, there seems 

 no alternative, to our apprehension, than to refer them to the 

 period subsequent to the sweeping out of that clay along the western 

 Wold-foot. They appear thus to be very nearly identical in age with 

 the beds / of the coast-section (fig. 1); but whether they be of 

 marine or fluviatile origin we have found no fossil evidence to 

 showt. 



In fig. 6 (ante, p. 161), which gives a condensed view of the de- 

 nudation features of central Lincolnshire, we meet with a similar in- 

 crease of denudation in the westerly direction, and see the Oolitic ridge, 

 or " cliff," as it rises from the Langworth, become entirely bare of the 

 Glacial clay. Comparing that section with fig. 5, we see the same ridge 

 equally denuded, with the added condition of all the Glacial clay be- 

 tween it and the Wold, which is present in fig. 6, swept away. Now 

 a similar series of sands to those occumng on the Wold-top, save that 

 their constituent material differs, occupies the Lincolnshire Oolitic 

 ridge ; and as the one starts from the denuded edge of the purple clay, 

 so does the other start from the denuded western edge of the Glacial 

 clay of mid-Lincolnshire, touching and, in places, shghtly overlapping 

 it. Commencing north of Lincoln, at Welton, these sands stretch, 

 past Spridhngton, Normanby, and Glentham, towards Waddingham. 

 After a short interval of omission, they begin again at Manton, 

 and swell out into ridges and dunes, which occupy the summit of 

 the " cliff," and near the latter place appear also to envelope it. 

 Stretching thence northward to within a few miles of the Humber, 

 these beds cover the ironfield of i!^orth Lincolnshire, and form ex- 

 tensive warrens near Manton, Bottesford, and Froddingham, reach- 

 ing in that part nearly to the edge of the outlier of Glacial clay near 

 Blyton, which is intersected by fig. 5. A continuation of these beds 

 seems also to occupy the Liassic escarpment at several places along the 

 brow of the Trent valley, and near the confluence of that river with 

 the Humber at Whitton ; but, not dealing with the structure of that 

 valley in this paper, we need not refer to them further. The position 

 of these beds, where they crown the Oolitic ridge, has a special in- 

 terest that can be best understood by the following section. 



* Those at Brigg are shown in fig. 5, under the symbol x. 



t Some of them, howeyer, contain deriyative fossils, the gravels on the north 

 side of North Care abounding with remains from the Posidonomya-bed, and 

 those on the south of it with Grryphcpa incurva. 



