434 PREHISTORIC EUROPE. 



which have been made for various purposes tell the same tale. 

 The general succession, however, according to Mr. de Eance, is 

 as follows : — 1 



1. Sand dimes. 



■2. Upper clay and silt, partly marine (Scrobicularia piperata) 

 and partly freshwater [Cyclas cornea). 



3. Upper peat and forest-bed. 



4. Lower clay and silt, partly marine (Scrobicularia piperata) 



and partly freshwater (Cyclas cor: 



5. Sand, with comminuted fragments of Cardium erfule and 



Tu rritella com m u n is. 



6. Lower peat and forest-bed. 



The bottom upon which the deposits rest is almost invari- 

 ably boulder-clay, but now and then they repose directly upon 

 the sandstones of the Triassic formation. Prom this succession 

 one might draw several conclusions bearing upon the general 

 geographical and climatic conditions of Britain, but for the 

 present we shall confine ourselves as closely as may be to the 

 purely local aspect of the evidence. First, then, we must 

 observe that here, as in Scotland, there is a strongly-marked 

 unconformity between the postglacial beds and the boulder-clay 

 that forms their pavement. Long before the trees of the lower 

 peat began to grow the ice-sheet had melted away, and its 

 bottom-moraine had been deeply incised by streams and rivers. 

 Xo trace of late glacial shell-beds has been met with under- 

 neath the peat — these, if they ever existed, have entirely dis- 

 appeared. TTe pass at once from the relics of an intensely 

 arctic condition of things to the remains of an abundant forest- 

 vegetation. This unconformity, therefore, indicates a gap in 

 the evidence. A very long time must have elapsed between 

 the final melting of the last great ice-sheet and the advent of 

 the Germanic flora. 



The lower peat varies in thickness from 2 inches to 10 feet, 



1 As the short account I give of these interesting deposits is merely meant for 

 comparison with the succession met with in other regions, I have not thought it 

 necessary to employ the local names used by Mr. de Ranee, Mr. Mellard Reade, 

 and others. 



