170 PREHISTORIC EUROPE. 



vast regions of Northern Europe buried under perennial snow 

 and ice, huge glaciers deploying upon the low grounds of France 

 and Italy, and creeping down the mountain-valleys of southern 

 Spain ; ice, in like manner, choking the upland valleys of 

 Corsica ; snow-capped mountains everywhere. Cold currents 

 flowing out of the Polar Ocean then laved the shores of North- 

 western Europe, bringing with them many arctic forms of life, 

 which occupied the area vacated by the temperate species as 

 these last found their way south to the coasts of Spain and the 

 Mediterranean. The walrus, now one of the rarest visitors to 

 Ultima Thule, frequented the English Channel, 1 where ice-rafts 

 were common, and into which rivers, flowing from perennial 

 snow-fields and glaciers, discharged their muddy waters. 



To give an adequate description of the facts upon which 

 these conclusions are based would lead me far beyond the 

 scope of this work, and I can find space for only a meagre out- 

 line of the subject. The history of the Glacial Period or Ice 

 Age is read in certain peculiar markings upon rock-surfaces ; in 

 the configuration of hills, the form of valleys, and the multi- 

 tude of lakes in alpine and northern regions ; in the character of 

 certain superficial accumulations of clay, gravel, sand, boulders, 

 and ddbris, which in those regions are more or less abundantly 

 developed ; in the presence of arctic and boreal shells and other 

 marine forms in the clay -deposits of low latitudes like our 

 own ; in the appearance of high-alpine and hyperboreal plants 

 in ancient peat-bogs ; and finally, in the present distribution 

 of the flora and fauna of Europe. These phenomena and the 

 mode in which they are interpreted have been discussed some- 

 what fully in the work mentioned below, 2 to which the reader 

 who wishes to study the subject in detail may refer. The 

 general results arrived at are all that I can attempt to give in 

 this place. 



The more conspicuous traces of the great glaciers and seas 

 of ice which formerly existed in Europe, are so prominent that 



1 See a paper by M. G. A. Defrance, Bull. Soc. Geol. France, 3 e Ser. t. ii. p. 164. 

 2 The Great Ice Age, etc. , 2d ed. 



