﻿8. V. Wood,jun. — American and British Surface-Geology. 543 



probably terminated direct in the sea, but on its eastern side it was, 

 as presently described, divided from the sea during part of the Upper 

 Glacial period bj a belt of land formed of the eastern parts of 

 Essex, Suffolk, and Norfolk. To the action of this glacier, when, 

 during its greatest extension, its principal mass rested on the great 

 Fen level, do I attribute the formation of that level itself; its edges 

 as above defined being on all sides, except the north, within twenty 

 miles of the Fen boundary ; and to the extrusion of its moraine 

 during recession do I refer the principal part of the chalky clay, the 

 rest having been accumulated by droppings in mass from ice which 

 floated in the sea during its greatest extension, as well as in the sea 

 that followed up its recession. As explained subsequently, a branch 

 from this glacier passing through the gorge of the Humber carried 

 out into Holderness nearly all the moraine engendered north of that 

 gorge, as well that engendered for a few miles south of it, the ice 

 against the Wold scarp drawing in from both sides of this gorge 

 to form a tongue which issued through the valley of the Humber. 

 Thus, as the glacier receded northwards, the moraine extruded be- 

 came less and less, so that before it receded to the latitude of the 

 Humber it had shrunk away from the Chalk Wold on its western 

 side, and there was no more chalky moraine to extrude. North 

 of Holderness, however, the glacier which came through the Vale 

 of Pickering, and passed over the lower ranges of the Wold for a 

 few miles inland of Flamborough, to which I have already adverted 

 as giving off bergs during the accumulation of the Contorted Drift, 

 but which, after the termination of that accumulation, ceased to give 

 off bergs, and which also had wasted back under the influences 

 which caused the Lincolnshire glacier to waste back and disappear, 

 still brought chalk debris, derived from the north scarp of the Wold, 

 but accompanied at first by a corresponding abundance of the hard 

 rocks which lie north of the Wold, and form the opposite side of the 

 Pickering trough.^ This morainic material is of a dark purple 

 colour in its lower part, changing to a more reddish purple upwards. 

 In its lower part it is full of rolled chalk mixed with the more 

 angular debris of hard rocks, and at its junction with the lead- 

 coloured chalky clay at its base (a of the sections and map) sheets 

 of it frequently alternate with sheets of the latter, showing, it seems 

 to me, that from this horizon at least upwards the clay of Southern 

 Holderness originated from the dropping process, and other forms 

 of marine deposit, and not by direct moraine extrusion. As we see 

 the succession upwards, exposed in the high cliff of Dimlington, and 



^ This trough is that lying between the north scarp of the Chalk "Wold and the 

 slope of the Eastern Moorlands formed mostly of rocky Jurassic beds. Its eastern 

 end is now blocked up by the last of the morainic clay which its glacier engendered, 

 so that the drainage flows in the opposite direction to that in which the moraine 

 travelled to the sea, viz. westwards and round the north-west angle of the Wold, and 

 thence southwards to the Humber, west of the Wold scarp. During the Contorted 

 Drift the Pickering glacier, I conceive, travelled perhaps 50 miles on both its sides 

 over chalk ; but at the period of the commencement of the pui-ple clay it had shrunk 

 back so that one side only touched the chalk, and this for a few miles only, and as 

 the purple clay deposit proceeded, it gradually shrank from the chalk altogether. 



