C— GEOLOGY 65 



that successive human industries extend farther northward's and north- 

 westwards as the ice retreated, although the re-advances of the glaciers 

 and flooding of the country temporarily drove the new invader back. 



If the time-succession of human industries recognised by our archaeo- 

 logical colleagues holds good (and in general it is becoming more firmly 

 established every year), we should expect the sequence pre-Chellian, 

 Chellian, Acheulian (Clactonian-Levalloisian), Mousterian, Aurignacian, 

 Solutrian, Magdalenian, Tardenoisian, and Neolithic, when traced 

 north-westwards across England, to display the phenomena known to 

 geologists as overlap. The newer deposits and human waves would 

 extend farther than the older, as the area was opened up to them by the 

 retreat of the ice. 



This is found to be broadly the case. I propose, therefore, to examine 

 the evidence for the contact of Early Man with stratigraphical horizons 

 in the east of England, then to endeavour to trace the history of events 

 across the Pennines to the Irish Sea, and thence to return by way of the 

 Severn Valley and the Thames. 



The praiseworthy labours, extending over a long period of years, 

 of the officers of the Geological Survey, and the work of numerous 

 other investigators, have served to show that, in the main, the topographic 

 features of Britain at the beginning of the Ice Age were similar to those 

 of to-day. Many of our important river- valleys, long thought to be 

 post-glacial, are now known to have been pre-glacial. They have been 

 modified in detail, it is true, and their terraces have in many cases been 

 proved to be of inter-glacial and late-glacial age. On the other hand, 

 glaciers have here and there acted as dams and, by forming glacier-lakes 

 and overflow channels, have caused permanent modification of river- 

 courses ; such eff'ects can, of course, be recognised without difficulty. 



The distinction formerly drawn between River-Drift Man (Early 

 Palaeolithic) and Cave Man (Late Palaeolithic) belongs almost to the 

 dark ages of the science. We recognise now that human occupation- 

 sites were largely determined by environment and topographic features. 

 If no caves were available, late Palaeolithic Man was as ready as his for- 

 bears to establish camps on open sites. River-Drift Man could not 

 inhabit caves in Britain for the very good reason that caves almost 

 exclusively occurred in areas protected by contemporary ice or snow. 



Our attempts at correlation may suitably begin in the east of England, 

 where the succession of Late Pliocene and glacial deposits is most 

 complete. 



East Anglia. 



The oldest deposit of undoubted glacial origin in Britain is found 

 as remnants which have escaped denudation in the east of Norfolk (where 

 it is known as the Norwich Brickearth), in Yorkshire (the Basement 

 Clay), and in Durham (the Scandinavian Drift). No remains of Man 

 have been found in it, and its age is inferred by reference to beds above 

 and below. Nevertheless, in the Crag deposits which underlie the 

 Norwich Brickearth and are referred to the later Pliocene, the late W. G. 

 Clarke, Mr. J. Reid Moir and Mr. J. E. Sainty have discovered worked 



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