TRANSACTIONS OF SECTION C. 571 



mouth of the Wanh. The author has, moreover, traced a trail of Neocomian 

 erratics for a hundred miles in the same direction from the plain of the Witham 

 to the neighbourhood of Ipswich. 



These facts suggest the existence of two confluent but distinct ice-streams 

 travelling, pan 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 

 Nortli 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 W, of Market Rasen, where the escarpment is 

 xinbroken 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 or 

 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 over- 

 spreading the higher ground which separates them. Moving along the strike of 

 the Oxford, clay'up the valley of the Ouse, it filled that i-egion with boulder-clay 

 of which the "matrix is prevalently Oxfordian; further to the north-west the 

 glacial drift contains a larger proportion of Liassic detritus. The boulder-clay 

 which covers the chalk region immediately below the crest of the escarpment is, 

 as a rule, very chalky, as is the drii"t to the west of the South 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 this climbed the Marlstone 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 Rugby and beyond. 



At one time it was believed that the crescentic moraines of York and Escrick 

 represent the greatest extension of the Teesdale ice. Now, the driftless area to 

 the south of York notwithstanding, it is admitted that the ice reached as far as 

 Barnsley and Doncaster ; the comparative absence of drift immediately to the 

 south of those places cannot, therefore, have any evidential value in the face of the 

 fact that chalky boulder-clay sets in again in great force still further to the south. 

 The enormous area covered by the moraine of the Great Eastern Glacier, 10,000 

 square miles in extent, is inconsistent with the view that it can have been wholly 

 due to ice crossing the Wolds at the two places named. We seem, therefore, 

 driven to admit the existence of a great ice-stream continuous from the mouth of 

 the Tees to the Fenland, and from the Pennines to the Yorkshire Moorlands and 

 the Wolds. 



The study of the glacial deposits of the East of England does not appear to 



