Rev. Edwin Hill — Lifting by Ice-melting. 1 5 



20 inches only.' A 6 ft. t)iick ice-slieet, after tliree-fouiths liad 

 melted away, could still transport a layer of nearly an inch. 



"The thickness of floe ice in Eaffins Bay is said to average 

 5 or 6 feet : elsewhere it is much thicker" (Bonney, Ice-ivork, p. 62). 

 In the Gulf of Eotlmia also it is 5 or 6feet(Lyell, Principles^ eh. xvi). 

 In the Antarctic Captain Scott estimates it as " in exposed sea under 

 8i- feet; where land precludes rapid circulation of water as much as 

 10 feet bj^ freezing alone; where snow accumulates any thickness 

 may be produced" (^Voyage of Discovery, vol. ii, p. 458). In 

 Shackleton's Heart of the Antarctic, vol. ii, p. 277, the maximum 

 thickness of sea ice is given as 7 feet. 



If a Glacial period began over our present England, would not 

 these effects be produced in such shallow sheets as some of the 

 Norfolk Broads? If subsidence should also occur, the Fens and other 

 low-lying tracts would experience tlie action. Many inland areas are 

 broad and level ; they, too, woidd be brought under it. Imagine the 

 Yale of York water-covered while ice-age temperatures pievailed ; 

 wouhl not much of its surface be lifted and carried into the Humber ? 

 Would not the Humber Estuary be kept filling up, and kept filling 

 up with material like the matrix of the Holderness Clays? 



Some peculiar features of some Glacial formations are what might 

 be expected if this action had been at work. 



Objects frozen to the bottom of an ice-crust, lifted and dropped 

 without stranding, would suffer no friction, no abrasion, no crushing. 

 Even should the ice strand, such objects being firmly frozen would be 

 in circumstances favourable for escaping injury. Ice lifting from 

 a bottom would lift its burden whole, liy its thaw the most delicate 

 shells might be deposited without chip or scratch. 



In stranding, as lias been said, objects attached to the lower 

 surface might be scratched. Also at the beginning of flotation there 

 would probably be some movement before complete removal. Such 

 also would grind or scratch. In the Chalky Boulder-clay the pieces 

 of chalk are mostly rounded, manj' scratched. 



Sedimentation in moving water is expected, ordinarily, to increase 

 in amount with the depth. Sedimentation from ice-rafts would not 

 be governed by depth. It would depend on the distribution over the 

 surface of sucli rafts, their loads, and their melting. If distribution 

 were uniform, deposit would be uniform ; it would cover the bottom 

 with a mantle of uniform thickness over plateau and valley alike. 



Material would be lifted in sheets, and might be so dropped. 

 Sheets, streaks, and pockets are frequent in Boulder-clays. I find it 

 easier to conceive even the long sheets of chalk in the Cromer clifl's to 

 have been lifted and dropped, than to be consequences of displacement 

 by thrust. Certainly, an ice-floe which could bear up a strip of 

 chalk 120 yards long and 10 deep (there is one such near Runton) 

 must have been large. But a floe twenty times its volume would be 

 large enough, and what would that be in Polar seas ? 



This paper treats of an action which would go on under water 



' This in fresh water. For salt water the necessary thicknesses wouUl be 

 less : about 25 and 15 respectively. With ice as fight as Captain Scott's 



estimate they would be smaller still. 



