178 



ISLAND LIFE 



PART I 



theory of repeated glacial epochs during the Tertiary 

 period. 



Evidences of Ice-action during the Tertiary Period. — The 

 Tertiary fossils both of Europe and North America indicate 

 throughout warm or temperate climates, except those of 

 the more recent Pliocene deposits Avhich merge into the 

 earlier glacial beds. The Miocene deposits of Central and 

 Southern Europe, for example, contain marine shells of 

 some genera now only found farther south, while the fossil 

 plants often resemble those of Madeira and the southern 

 states of North America. Large reptiles, too, abounded, 

 and man-like apes lived in the south of France and in 

 Germany. Yet in Northern Italy, near Turin, there are 

 beds of sandstone and conglomerate full of characteristic 

 Miocene shells, but containing in an intercalated deposit 

 angular blocks of serpentine and greenstone often of 

 enormous size, one being fourteen feet long, and another 

 twenty-six feet. Some of the blocks were observed by Sir 

 Charles Lyell to be faintly striated and partly polished on 

 one side, and they are scattered through the beds for a 

 thickness of nearly 150 feet. It is interesting that the 

 particular bed in which the blocks occur yields no organic 

 remains, though these are plentiful both in the underlying 

 and overlying beds, as if the cold of the icebergs, combined 

 with the turbidity produced by the glacial mud, had driven 

 away the organisms adapted to live only in a comparatively 

 warm sea. Rock similar in kind to these erratics occurs 

 about twenty miles distant in the Alps. 



The Eocene period is even more characteristically tropical 

 in its flora and fauna, since palms and Cycadacese, turtles, 

 snakes, and crocodiles then inhabited England. Yet on 

 the north side of the Alps, extending from Switzerland to 

 Vienna, and also south of the Alps near Genoa, there is a 

 deposit of finely-stratified sandstone several thousand feet 

 in thickness, quite destitute of organic remains, but con- 

 taining in several places in Switzerland enormous blocks 

 either angular or partly rounded, and composed of oolitic 

 limestone or of granite. Near the Lake of Thun some of 

 the granite blocks found in this deposit are of enormous 

 size, one of them being 105 feet long, ninety feet wide, 



