WOOD AND ROME LmCOLNSHIRE AND S.E. YORKSHIRE. 175 



ly. The Dentjdation-beds and Denudation-features of York- 

 shire AND Lincolnshire. 



The denuded westerly edge of the purple clay on the Wold-top is 

 occupied by thick masses of sand and gravel, which, near Specton, 

 pass over the edge of the clay. These, especially towards their base, 

 although they rest extensively on the chalk, are principally com- 

 posed of fragments of older Secondary, Palaeozoic, and Metamorphic 

 rocks, derived from the destruction of the purple clay, and containing 

 very little of the material (the chalk) on wliich they rest, notwith- 

 standing that this chalk rises towards the north-western angle of the 

 Wold to nearly twice the height, where the greatest quantity of these 

 sands occur. Setting in near Specton and Eeighton, they occur in 

 numerous mounds of considerable depth and extent along the Wold- 

 top there, and at Hunmanby New Mill. Thence, away towards the 

 north-western angle of the Wold, they are scattered in a few places 

 along its summit. A mass 50 feet thick, resting, we believe, on the 

 purple clay, occurs under Speeton Mill, at an elevation of 457 feet. 

 Another patch, some few square furlongs in extent, occurs at the 

 north-west angle of the Wolds, at Thixendale Grange, at an elevation 

 of about 700 feet, while others exist at elevations of about 600 feet, at 

 Timber and Huggate*. These appear to be the earliest deposits, in 

 this part, of the Postglacial or general denudation- sea. Another 

 extensive series of sands, with gravel, occurs along the Wold-foot 

 from near Muston, through the great valley, as far as Malton, which, 

 at East Plotmanby (near Muston) was found, in boring, to be up- 

 wards of 60 feet thick, with an unknown depth of shingle beneath. 

 These Wold-foot sands, with gravel, are composed principally of 

 local materials. Cretaceous and Oolitic, and, not having been 

 formed until after the emergence and denudation of the Wolds, 

 are thus newer than the sands on the Wold-top f. As we do not 

 discover any traces of the Hessle clay along the north foot of the 

 Wold, it might be inferred that its waters never penetrated the vale 

 of Pickering ; nevertheless the considerable elevation which that 

 clay attains along the eastern slope of the Wolds, and especially at 

 Swanland, three miles north-west, and at Melton Ross, ten miles 

 south of Hessle, renders it difficult to suppose that this vale could 

 have escaped being penetrated by the Hessle-clay waters through 

 the gorge at Hutton, near Malton, and over the lower part of the 

 ground around that place. In such a case it would seem to follow 

 that these north Wold-foot gravels are of an age posterior to the 

 sweeping out of the Hessle clay from that trough, unless they be, 



* The patch at Huggate rests on the only outlier of the purple clay that we 

 have been able to detect over the high Wolds, with the exception of a small one 

 at Pimber ; so complete has been the denudation there. This outlier, however, 

 at so great an elevation, satisfactorily proves the original envelopment of the 

 Wold in the purple clay. We are under obligations to Mr. Mortimer, of 

 Fimber, for the knowledge of the existence of these outhers. 



t Although this appears to us to be a legitimate inference in this case, we are 

 far from admitting that, as a general rule, levels are to be taken as evidence of 

 the relative ages of Postglacial deposits, or that anything answering to general 

 high- and low-level gravel-periods ever existed. 



