382 PREHISTORIC EUROPE. 



carried down in flood-time immense quantities of fine mud, with 

 which they covered wide areas in the low grounds. Such, in a 

 few words, were the physical conditions of " late glacial times." 



Tor reasons which will become obvious as we advance in 

 oiir inquiries, the passage from those times to the Postglacial 

 Period cannot always be traced. There would often appear to 

 be a gap or hiatus in the evidence, for frequently we pass at once 

 from true glacial beds into overlying accumulations of postglacial 

 age, which give proofs of very different climatic conditions. 

 Sometimes, for example, we find that clays well charged with 

 arctic shells are overlaid directly with peat containing abundant 

 roots and trunks of large oaks and other trees. In this case it 

 is clear that certain evidence is wanting. We may be sure that 

 the climate could not have changed in the twinkling of an eye. 

 The bed of an arctic sea has been converted into dry land, and 

 the climate has become temperate, but the deposits in which the 

 gradual amelioration of climate might have been traced are 

 wanting. Numerous examples of this phenomenon occur in our 

 maritime regions, as I shall point out presently. In the inland 

 districts there is often a similar appearance of a want of conti- 

 nuity between late glacial and postglacial times. But the want 

 of continuity is in such cases only apparent, as certain discoveries 

 made in recent years have clearly demonstrated. This will come 

 out clearly, I hope, in the sequel : meanwhile, we must take a 

 glance at the evidence supplied by the postglacial deposits of 

 our islands and the Continent before we attempt to grapple with 

 the more general questions which such a review of the facts 

 will suggest. Confining myself first to a mere description of 

 details, I shall briefly indicate the conclusions to which these 

 directly lead, and, thereafter, I shall sum up the general evidence 

 and endeavour to discover what light it throws upon the succes- 

 sion of climatic and geographical changes which characterised 

 Europe in postglacial times. It will be most convenient to 

 begin with the evidence supplied by our own country, and as the 

 succession of postglacial deposits and the relation of these to 

 accumulations of glacial age are perhaps better displayed in 



