GEOGRAPHICAL EVOLUTION 359 



grim and defiant of the elements. Its veins of quartz, 

 felspar, and hornblende project from every boss and crag 

 like the twisted and knotted sinews of a magnificent torso. 

 Well does the old gneiss of the north deserve to have been 

 made the foundation-stone of a continent. 



What was the character of the vegetation that clothed 

 this earliest prototype of Europe is a question to which at 

 present no definite answer is possible. We know, however, 

 that the shallow sea which spread from the Atlantic south- 

 ward and eastward over most of Europe was tenanted by 

 an abundant and characteristic series of invertebrate ani- 

 mals trilobites, graptolites, cystideans, brachiopods, and 

 cephalopods, strangely unlike, on the whole, to anything 

 living in our waters now, but which then migrated freely 

 along the shores of the Arctic land between what are now 

 America and Europe. 



The floor of this shallow sea continued to sink, until 

 over Britain, at least, it had gone down several miles. Yet 

 the water remained shallow because the amount of sedi- 

 ment constantly poured into it from the north-west filled it 

 up about as fast as the bottom subsided. This slow subter- 

 ranean movement was varied by uprisings here and there, 

 and notably by the outburst at successive periods of a great 

 group of active submarine volcanoes over Wales, the Lake 

 district, and the south of Ireland; but at the close of the 

 Silurian period a vast series of disturbances took place, as 

 the consequence of which the first rough outlines of the 

 European continent were blocked out. The floor of the 

 sea was raised into long ridges of land, among which were 

 some on the site of the Alps, the Spanish peninsula, and 

 the hills of the west and north of Britain. The thick mass 

 of marine sediment was crumpled up, and here and there 

 even converted into hard crystalline rock. Large enclosed 

 basins, gradually cut off from the sea, like the modern 

 Caspian and Sea of Aral, extended from beyond the west 

 of Ireland across to Scandinavia and even into the west of 

 Russia. These lakes abounded in bone-covered fishes of 

 strange and now long-extinct types, while the land around 

 was clothed with a club-moss and reed-like vegetation 

 Psilophyton, Sigillaria, Catamite, etc. the oldest terrestrial 



