264 THE BOULDERS OP THE CAMBRIDGE DRIFT. [Aug. I909, 



received from Mr. P. W. Harmer, who was unfortunately unable 

 to be present : — 



' The occurrence of igneous erratics in the Glacial deposits of the Fenland 

 seems at first sight anomalous. As far back as 1858, Trimmer had noted the 

 existence of two Boulder-Clays in the Suffolk cliffs, the lower of which he 

 identified with that containing Scandinavian blocks which extends over Northern 

 Europe ; the upper characterized by Jurassic debris, which he had traced 

 towards the west. Subsequent investigation has confirmed this view, and has 

 shown that East Anglia was twice invaded by ice, first directly from the North 

 Sea, originating the Contorted Drift with its igneous boulders, Scandinavian or 

 North British ; and next by an inland ice-stream, the moraine of which (the 

 Chalky Boulder-Clay) is prevalently of a Cretaceous and Jurassic character. The 

 latter contains, however, although rarely, igneous boulders of similar character 

 to those of the Contorted Drift. 



'In a paper, now in the press, I am endeavouring to explain the existence 

 of North Sea drift in a deposit which is plainly of inland derivation. The 

 North Sea drift occupies a large and continuous area in the north-east of 

 Norfolk, but it terminates abruptly to the south along a line running across the 

 country from north-west to south-east, being replaced by the morainic deposit 

 of the inland ice-stream (the Chalky Boulder-Clay), which lies side by side 

 with it, and at the same level. The older deposit was ploughed out, I believe, 

 by the advance of the inland glacier, and was incorporated in the moraine of the 

 latter. 



' No Contorted Drift is known in the Fenland region, although its former 

 presence there seems to be indicated by the Scandinavian and other such 

 erratics recorded by the Authors. It does not seem probable that when the 

 North Sea ice overran Norfolk, it could have failed to enter the Fenland by 

 any opening then existing in what is now the Wash. The Wash gap was 

 closed, however, in my opinion, at the later or Chalky Boulder-Clay stage, by 

 the glacier which carried the Cretaceous, Neocomian, and Kimmeridgian 

 material into Mid-Suffolk. Neocomian erratics of Lincolnshire type are 

 exceedingly common in West Norfolk, and they may be traced thence in a 

 continuous trail to the south-east, but there is no evidence whatever of any 

 ice-drift during the Chalky Boulder-Clay period, south-westwards from the 

 Wash. It would seem to follow, therefore, that the igneous boulders, not 

 only of the Chalky Boulder-Clay of Norfolk, but of the Fenland also, are 

 derivative from some North Sea deposit of Contorted-Drift age, formerly 

 existing in the regions in question.' 



Prof. W. W. Watts remarked that, although the Authors had 

 wisely refrained from much theory, they had obtained a store of 

 facts, which would do much to influence future theories. In his 

 judgment the ice-sheet theory seemed to present a more consistent 

 story of the events of the Glacial Epoch than any other known to him. 



Mr. Pastall, replying on behalf of both Authors, thanked the 

 Fellows for their kind reception of the paper. In reply to the 

 President, he stated that, while aware of the wide distribution of 

 Red Chalk over the district, it was to its association with bored 

 pebbles of hard white Chalk and bored shells of Gryphcea that the 

 Authors attached importance. This association appeared to be con- 

 fined to the eastern and southern parts of the district. With regard 

 to the method of distribution of erratics, the Authors, although not 

 fanatical upholders of the land-ice theory, had been led by the 

 facts to adopt this view in their conclusions. Attention had been 

 paid to the possibility of derivation of material from the sea-floor, as 

 suggested by Mr. Lamplugh. Owing to the lateness of the hour, 

 he was unable to deal fully with the points raised by other speakers. 



