Notices of Memoirs — Papers read at British Association. 469 



These facts sujj;-gest the existence of two confluent but distinct 

 ice-streams travelling, pari passu, from N.W. to S.E., that which 

 occupied the Jurassic plain being sufficiently the stronger to thrust 

 on one side the ice descending from the Wolds, diverting it towards 

 Norfolk, mounds of Chalky Boulder-clay more or less parallel with 

 the escarpment being accumulated between the two as a medial 

 moraine near Horncastle. This view explains why, at the period in. 

 question, the North Sea ice was unable to enter East Anglia through 

 the Wash Gap. 



The absence of the intensely Chalky Boulder-clay of South 

 Lincolnshire from the Lincolnshire plain to the west of Market 

 Easen, where the escarpment is unbroken and more than 500 feet 

 high, indicates that no ice overflowed the Wolds near that place, nor 

 did any cross from the North Sea to the north of the Humber. 



It must therefore have been the region south of that river, and 

 north of Caistor, where the Wolds have been broken up and eroded, 

 which supplied the grey flint and hard chalk (other than that of the 

 Norfolk Drift), which is found everywhere in the Chalky Boulder- 

 clay over such an enormous area. So prodigious is the total amount 

 of this debris that, were it brought together, it would almost bridge 

 over the depression now dividing the Lincolnshire from the Yorkshire 

 Wolds. 



From the Fenland the Great Eastern glacier fanned out in all 

 directions : to the east over Suffolk, overflowing also the chalk 

 escarpment from Newmarket to Hitchin, from which it travelled 

 down the dip-slope south-eastward into Essex, and southward 

 towards Finchley and St. Albans. To the south-west it occupied 

 the basins of the Welland, the Nene, and the Ouse with a confluent 

 ice-sheet overspreading the higher ground which separates them. 

 Moving along the strike of the Oxford Clay up the valley of the Ouse, 

 it filled that region with Boulder-clay of which the matrix is 

 prevalently Oxfordian ; further to the north-west the glacial drift 

 ooiitains a larger proportion of Liassic detritus. The Boulder-clay 

 wliich covers the chalk region immediately below the crest of the 

 escarpment is, as a rule, very chalky, as is the drift to the west of the 

 Lincolnshire Wolds, and for the same reason, viz., that it was 

 ^principally the upper and cleaner portion of the ice-sheet which 

 mounted the slopes of the chalk hills. Some Jurassic debris from 

 the Fenland was, however, carried over into Essex, but not enough 

 to give the drift of that region a typically Jurassic character. 



Another and an important branch of the Great Eastern glacier 

 passed up the Trent basin. One portion of tliis climbed the 

 iiiarlstone escarpment near Grantham, and spread Chalky Boulder- 

 clay over the high land to the south of that place ; another part 

 followed the Trent valley towards the south-west until it met the 

 ice streams of the Dove and the Derwent, the combined ice-flow 

 being thence southwards up the valley of the Soar. Glacial drift 

 containing, on the one hand, Pennine and Mount Sorrel erratics, and, 

 on the other, Jurassic and Cretaceous debris, may be traced for many 

 miles to the south and south-west of Leicester towards Kugby and 

 beyond. 



