THE PLEISTOCENE OR GLACIAL PERIOD. 483 



phenomena, such as submerged peat bogs, meadows, forests, etc., 

 show. 



It is not improbable that movements of equal magnitude have 

 affected the interior regions of the continent, but except about the 

 lakes, there is no datum plane like the sea-level to which these changes 

 may be readily referred. In a few places, notable local deformation 

 is known. In western New York * and Ohio, the solution of under- 

 lying gypsum and salt is suspected of being the occasion of some of 

 the slight deformations winch have been observed. 



Foreign. 



The salient points in the glacial history of Europe have already 

 been sketched and some indication has been given of the extent of 

 the deployment of ice in other continents. It need only be added 

 here that outside the areas affected by the ice, there are, in all con- 

 tinents, subaerial accumulations of talus, wash, and creep at the bases 

 of mountains, deposits of alluvium in the valleys, and eolian deposits. 

 About the coasts at many points on various continents there are marine 

 sediments ranging from a few feet to hundreds of feet above sea-level. 

 In Europe there are cave deposits regarded as Pleistocene, which are 

 of especial interest because they contain human relics, probably the 

 oldest known. The relics consist of rude stone implements, bones of 

 mammals with human markings on them, and bones of human beings. 



The Ljfe of the Pleistocene Period. 



Destructive effects cf glaciaticn. — Just as the great ice deploy- 

 ment was the supreme physical event of the Pleistocene period, so 

 the effect of glaciation on the life of the times was the foremost sub- 

 ject of biological importance. It is altogether reasonable to assume 

 that the burial of several million square miles beneath successive mantles 

 of ice, abetted by the southward extension of attendant cold zones and 

 cold currents, wrought great destruction of life, and forced upon what 

 survived no little modification. The logic is so cogent that we must 

 believe it to be true; but several embarrassments attend an attempt 

 to statistically demonstrate the conclusion, and to interpret its pre- 

 cise nature. For concrete proof of the effects, we naturally resort to 



1 Gilbert, Proc. Am. Ass. Adv. of Sci., Vol. XL, p. 249. 



