318 SUMMARY OF GEOGRAPHICAL EVOLUTION. [CHAP. XIV. 



place. These movements, so far as we can judge, produced 

 the geographical conditions represented in Plate XIII., Bri- 

 tain then forming a broad and roughly triangular promon- 

 tory based on the northern part of France and ending 

 northwards beyond the Shetland Isles. The western coast- 

 line lay probably between the contours of 200 and 300 

 fathoms, at any rate off the north-western coast, so that 

 the isthmus between Scotland and the Faroe Isles was 

 completely submerged. The eastern coast, however, along 

 the western border of the newly-formed North Sea, ap- 

 proximated closely to the outline it now presents. 



Before the close of the period, indeed, the agencies 

 which had been busily and continuously engaged through- 

 out the whole of antecedent Tertiary time in modelling 

 and carving the surface of the British region, had almost 

 completed their task. All the principal physical features 

 of our islands had then been developed, and the general 

 aspect of Britain in later Pliocene time can hardly have 

 differed very much from that of modern Britain, except that 

 it stood bodily higher above the level of the ocean, so that 

 the seas and channels which now separate our islands from 

 one another and from France were then in the condition 

 of fertile plains and valleys. In minor details there was 

 of course a considerable difference ; the North Downs, and 

 probably also the South Downs, were continuous across 

 what is now the head of the English Channel, and the 

 surface features of the country, in the absence of the 

 superficial clays and gravels which now cover such large 

 areas, must necessarily have had a different aspect. 



The Pliocene surface had of course its terrestrial and 

 fluviatile deposits ; the long-continued action of wind, 

 frost, rain, and rivers must have resulted in the formation 

 of long slopes of debris among the hills, of thick deposits 

 of sand and gravel in the valleys, of deep beds of clay and 

 marl in the lake-basins, and in the production of a thick 



