64 SECTIONAL ADDRESSES 



conditions as having been inaugurated after the passing of the Ice Age 

 is still seen in the practice of referring the terraces of existing rivers to 

 post-glacial times. When, therefore, a river-terrace is described as 

 post-glacial because it is proved to be of later date than the local boulder 

 clay, we should remember that this use of the term post-glacial has 

 only a local significance and is therefore loosely applied. The very 

 extent of the broad and elevated areas of ancient river-gravels is evidence 

 of conditions capable of giving rise to rivers of great volume. If such 

 conditions were due to a very heavy rainfall, they would be accompanied 

 by an exceptionally luxuriant flora ; but of this we have no evidence. 

 More probably, therefore, the volume of water arose from melting ice. 



It is because the work of the last twenty years has so greatly resolved 

 the difficulty of co-ordinating the evidence of Man's activities with 

 that of the advance and retreat of the glaciers, that I have elected in 

 this address to review our state of knowledge of the subject. This is 

 not to say that the difficulties have all been overcome, but the reception 

 accorded to an attempt which I made recently at scavenging among the 

 confused deposits and literature of East Anglian geology and prehistory 

 encourages me to make another effort. It can but afford an incentive 

 to vigorous discussion and the consequent establishment of relationships 

 at present obscure. 



As has frequently happened in British stratigraphical history, the 

 situation of our country has provided exceptionally valuable imforma- 

 tion for use in correlation. Special conditions resulted from the position 

 of the greater part of the British Isles as an area just beyond the margin 

 of successive glaciations ; in addition, a remarkable variety of human 

 industries has been found. Our cultural evidence cannot vie with that 

 of the caves of France and northern Spain, with their richness in painting 

 and sculpture, but we may claim that the prehistoric remains in Britain 

 have more illuminating contacts than those abroad. 



As is well known, an elevation of the British area of little more than 

 100 feet would be sufficient to re-establish land-connection with the 

 Continent by way of the east and south-east of England. We have 

 good evidence in support of the view that in late Pliocene times such 

 a connection existed, and that the area now occupied by the North Sea 

 was land drained by a large forerunner of the present River Rhine, of 

 which the Thames and other rivers of the east of England were merely 

 tributaries. The ' warm ' and southern fresh- water shell, Corbicula 

 fluminalis, now living in the Nile, Euphrates, and other southern rivers, 

 had already established itself in streams that fed the late Pliocene repre- 

 sentative of the North Sea. Under the climatic oscillations which followed 

 during the Glacial Epoch, it appears to have retreated southwards before 

 the ice-advance and only to have returned to our area in Acheulian inter- 

 glacial times. 



Wherever the cradle of Man may have been, Asia or Africa, the evidence 

 of prehistoric stations shows that the waves of his successive migrations 

 advanced north-westwards across Europe. The British Isles were his 

 Ultima Thule, along the road to which he sought his prey. His advance 

 was determined by the extent to which the country was ice-free, for we find 



