CHAPTER XIII. 

 ICENIAN PERIOD. 



PLEISTOCENE EPOCH. 



E a detailed account of the deposits of this period I 

 must refer the reader to my previous volume on " His- 

 torical Geology," and to Mr. H. B. Woodward's " Geology 

 of England and Wales." For my present purpose it is only 

 necessary to give such a summary of what is known re- 

 specting the distribution and succession of these deposits 

 in England, Ireland, and Scotland as may afford a basis 

 for considering the physical and geographical changes which 

 took place during the period. 



The Pleistocene deposits are generally treated under the 

 heads of Glacial and Post-glacial Beds by British writers, 

 but, though this is a convenient division in dealing with 

 the deposits of a limited area, it becomes misleading when 

 those of a larger region are compared with one another, as 

 for instance those of southern and northern England. The 

 so-called Ice Age or Glacial Period must be regarded as a 

 special episode or phase of Pleistocene time, and though its 

 influence may be traceable over a large area of the earth's 

 surface, yet the deposits which owe their origin to the 

 direct action of ice are limited to certain regions within the 

 40th parallels of latitude in both hemispheres. 



There is no doubt that what took place in the Glacial 

 period was simply an extension of the glacial conditions 

 which now exist in the polar regions. The fauna of the 

 Pliocene Beds affords evidence of the gradual refrigeration 



