GLACIAL EPOCH. 



167 



elevations ; icebergs, summer after summer, drift over the 

 waters ; and the sea, attacking the soft emerging shores, re- 

 assorts and re-deposits the sands, gravels, and clays of the 

 older glacial epoch. By-and-by the deposits become fossili- 

 ferous, showing that the ocean was tenanted by shell-fish, 

 seals, whales, and other creatures, whose habitats are now 



Skeleton of Seal (Phoca vitulma '<). from the Brick-clay of Suatheden, Fifeshire ; 

 a, detentition of do. 



the icy regions of the arctic circle. Upward, still upward, 

 the land emerges, evincing in its old water-lines and raised 

 beaches the successive steps of its uprise, till ultimately 

 the continents of the northern hemisphere assume, within 

 appreciable limits of current mutation, the configuration 

 and climatology they now present. As the continents 



;i 4 j 



Boreal Shells in the Drift of the Clyde. SMITH. 



1, Astarte borealis ; 2, Leda oblonga ; 3, Saxicava rugosa; 4, Pecten islandicus ; 

 5, Natica clausa ; 6, Trophon clathratum, 



emerge and the land surfaces augment, as new atmospheric 

 and oceanic currents are established, and as the post-ter- 



L 



