76 SECTIONAL ADDRESSES 



Flamborough, in a late-glacial deposit, which he regards as the equivalent 

 of the coastal Hessle Boulder Clay, compare closely with the implements 

 from the Hunstanton Boulder Clay, although the officers of the Geological 

 Survey would prefer to regard the deposit in which they were found 

 as a local kind of Coombe Rock. In the gravels of Kelsey Hill and 

 Burstwick near Hull, long famous for their molluscan faunas (which 

 include Corbicula fluminalis), and regarded by geologists as genetically 

 connected with and overlying a Purple Boulder Clay, Mr. Burchell has 

 found Early Mousterian artefacts ; as he rightly points out, the strati- 

 graphical relationships may thus be similar to those at Hoxne, since he 

 found below the gravels at one locality a boulder clay which he identified, 

 from its lithological characters, as Lower Purple Boulder Clay. 



Sections have been described where two beds of the Purple Boulder 

 Clay, separated by sands and gravels, have been observed. Prof. 

 Kendall and Drs. HoUingworth, Raistrick, and Trotter are now inclined 

 to regard these two boulder clays as due to separate glaciations, with 

 an intervening interglacial phase. Dr. Raistrick would correlate the 

 Lower Purple Boulder Clay with the early maximum of the Yorkshire 

 Dales glaciation, and the Upper Purple Boulder Clay with the Vale of 

 York maximum (Main Dales glaciation) and the passage of the Lake 

 District ice over Stainmore. Drs. HoUingworth and Trotter agree 

 in linking the Upper Purple Boulder Clay with their Early Scottish 

 glaciation and the eastward travel of Lake District ice. Thus Yorkshire 

 would appear to have suffered four glacial episodes (as Clement Reid 

 originally thought), comparable with those of East Anglia, the Lower 

 and Upper Purple Boulder Clays corresponding to the Chalky-Jurassic 

 Boulder Clay and Upper Chalky Drift, respectively. The return of 

 Corbicula fluminalis to the British area here appears to be of correlative 

 value, for the Kelsey Hill gravels containing it overlie the Lower and 

 underlie the Upper Purple Boulder Clay ; but if, as Lamplugh was 

 inclined to think, the specimens were glacially derived from a river- 

 deposit lying towards the east, the gravels might be associated with the 

 retreat of a later ice-sheet, possibly that which formed the Upper Purple 

 Boulder Clay. The present archaeological evidence does not support 

 the latter view. Moreover, recent work by Mr. W. S. Bisat shows 

 that both Upper Purple Boulder Clay and Hessle Clay overlie the Kelsey 

 gravels. 



In one respect, however, the Yorkshire succession supplements our 

 knowledge of that in East Anglia, for below the Basement Clay or most 

 ancient Till at Sewerby is a preglacial cliff and beach containing the 

 remains of hippopotamus, the straight-tusked elephant and the leptorhine 

 rhinoceros. These mammalian forms are often associated with imple- 

 ments of Chellian Man, although they may persist to later times. At 

 first sight it appears that here we have another link with the Cromer 

 succession, if the beach is correlated with the Cromer Forest-bed. In 

 the sand-dunes overlying the beach but underlying the Basement Clay 

 appears a fauna consisting of mammoth, urus, bison and Irish elk. The 

 sand-dunes, together with a bed of chalk-rubble below them, are evidence 

 of an old land-surface. 



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