﻿544 S. V. Wood,jun. — American and British Surface-Geology. 



that soutli of Mappleton, where the uppermost part of the purple 

 clay has escaped the denudation which, prior to the Hessle beds, 

 destroyed it elsewhere to the south of Bridlington, the rapid decrease 

 of the chalk debris is very marked, but the decrease of the debris of 

 the hard rocks north of the Wold is much less conspicuous. ' Still, 

 even this diminishes, and though it continues in the clay of the 

 upper parts of these two cliffs, it becomes so scant that in the 

 uppermost part where the chalk debris has wholly ceased, and 

 where the Hessle clay with its subangular chalk debris wraps over 

 it, there is very little debris of any kind in the clay. It is in fact 

 a stiff mud, much resembling, save that it is stiflfer and uncontorted, 

 and has no chalky sediment intermixed in it, the Contorted Drift of 

 Cromer Cliff, which is generally conceded to be a marine silt, though 

 nearly destitute of organic remains. It is, I think, more than doubt- 

 ful whether any of the clay without chalk south of the Pickering 

 trough is of direct morainic origin, either as originally extruded, or 

 as dropped. It seems to me, though produced from the grinding 

 of the glacier-ice, to have been distributed by marine agency, ac- 

 companied by the dropping of erratics from floe-ice ; for not only 

 is this clay full, though at no particular horizon, of lenticular beds 

 of sand (c and d! of Section I.) — a feature which the true morainic 

 chalky clay of East Anglia lacks — but it presents the most marked 

 contrast to the small moraines of pure rolled chalk (c of the same 

 section) which underlie it, and occupy ravines or gullies in the chalk 

 floor where it rises above the beach from Bridlington northwards. 

 These small moraines are evidently connected with the purple clay 

 containing much chalk of the cliffs south of Mappleton (c of the 

 section), the place of which they occupy relatively to the clay with 

 little and no chalk {d) that overlies both ; and having been formed 

 beneath the Pickering glacier while it still rested on the north- 

 eastern extremity of the Wold after the termination of the chalky 

 clay formation, they seem confirmatory of the mode in which the re- 

 treat of the ice took place, as indicated by the other phenomena 

 previously discussed. 



As this mud-like clay {d) caps the cliffs continuously northwards 

 from Bridlington to the mouth of the Pickering trough (which it 

 blocks up) , and for several miles attains elevations between 350 and 

 400 feet, it seems to me to indicate that when the Pickering glacier 

 by shrinking back gave rise to its accumulation, Yorkshire must 

 have been submerged to that extent. 



The recession of this glacier through the Vale of Pickering after 

 the disappearance of the glacier which produced the chalky clay is 

 thus, it seems to me, very clearly indicated ; as well as two corol- 

 laries ; the first of which is that, when the chalky clay was in pro- 

 gress of accumulation, the contemporaneous moraine that passed 

 through the Vale of Pickering was left out in the sea beyond our 

 present shores ; and the second of which is that, since the further 

 north the latitude the later must have been the recession, the 

 Glacial clay of the northernmost English counties is later than all 

 this of Holderness, except possibly that which, wholly destitute of 



