24 



groovings and scratches on the rocks of our mountain districts, 

 heaps of moraine rubbish in the valleys such as we see now at the 

 termination of the Swiss glaciers, and enormous deposits of " drift 

 clay" collected by the ice in its travels and deposited as the 

 glacier melted. 



All through Miocene and Pliocene times the temperature had 

 been gradually lowering, as we see by the increasing prevalence of 

 Arctic forms of life and the lessening numbers of such as are now 

 found in warm seas. As the cold developed itself more and more 

 southwards and at last produced the ice masses, so the animals and 

 plants were gradually driven in the same direction until the rein- 

 deer grazed on the plains in the south of France. Whenever the 

 cold moderated, as it did more than once, animal life swung 

 northwards, and the mammoth and hippopotamus were preyed 

 upon by hyenas as far north as Yorkshire. From river gravels and 

 from cave deposits all over our land we have extracted a rich 

 harvest of animal remains, sometimes of curiously mixed families 

 owing to the variabihty of climatic conditions. 



Sir C. Lyell, in his " Antiquity of Man," describes the following 

 successive geographical states of the British and adjoining areas : — 

 First, a continental period when tbe upheaving movement at the 

 close of Pliocene times continued until the land stood at a much 

 higher level than it does at present. " Britain formed part of the 

 mainland, and the bottom of the old Pliocene sea became the 

 feeding grounds of the animals which hare left their remains in 

 the Forest Bed, and all over and around the Dogger Bank. Ireland 

 must also have been united to Britain to allow of their finding their 

 way so far to the west." At the same time, and perhaps partly in 

 consequence of this elevation the temperature was lowered, and 

 the country was invaded by numerous species of mammals from 

 the north and west of Asia, where of course the climate was still 

 more extreme. At length it became too cold even for these ; snow 

 and ice covered all the higher portions, while huge glaciers radiated 

 from Scotland, Cumberland, and Snowdon, the marks of which I 

 just now mentioned. Probably we owe the Scandinavian portion 

 of our flora to this time. 



Then set in a period of submergence ; the shore-line retreated, 

 and the glaciers deposited the boulder clay as they melted, and 

 portions of them drifted off as icebergs as far at least as the 

 valley of the Thames. Arctic mammals came in, driven gradually 

 southward, and the Scandinavian plants " which occupied the 

 lov/er grounds during the previous continental period may have 

 obtained exclusive possession of the only lands not covered with 

 perpetual snow." (Ant. Man. p. 331). 



