Boulder- Clay. 395 



prevailed in these regions under some form or other. 

 A minority of persons who excel in the art of doubting 

 will of course dissent for a time, but the proof is too 

 strong to be withstood by commonplace minds. On^the 

 whole, also, it would appear that the complete glacial de- 

 posits of the east of England consist of Lower and Upper 

 Boulder-clays, between which there lie stratified sands 

 and gravels containing sea-shells, and that these strata 

 were deposited in the sea during a temporary intermis- 

 sion of the cold of a Glacial Epoch. Shells, sometimes 

 fragmentary and sometimes entire, are also found 

 plentifully enough in the Boulder-clays of Holderness 

 and elsewhere. 



In older times the origin of these Boulder-clays was 

 attributed chiefly to icebergs that, laden with moraine 

 matter, broke from glaciers that descended, during a 

 period of partial submergence, to the sea, and which, 

 floating south and melting, scattered boulders and 

 stony debris mixed with fine mud across the bottom of 

 the sea. 



But of late there has been a tendency in some 

 writers to attribute the origin of all, or almost all of the 

 British Boulder- clays to the direct action of glaciers, 

 and to look upon them as ground-moraine matter, the 

 moraine profonde of Swiss and French authors, which 

 is supposed to have a modern parallel in the vast quan- 

 tity of debris, believed to underlie and be pushed for- 

 ward by the mighty ice-sheet that passes seaward from 

 the great basin of central Greenland, and finds its vents 

 through unnumbered fiords into Baffin's Bay. On these 

 grounds both the Boulder-clays of the east of England, 

 are looked upon by Mr. Skertchly as having been 

 formed by the direct action of glaciers, the upper 

 Boulder-clay being the work of the larger and later ice- 



