600 THE POPULAR SCIENCE MONTHLY. 



a small fraction of the material so removed, for the sea of that 'ancient 

 time spread over nearly the whole of Europe eastward into Asia, and 

 everywhere received a tribute of sand and mud from the adjoining 

 shores. 



There is perhaps no mass of rock so striking in its general aspect 

 as that of which this northern embryo of Europe consisted. It lacks the 

 variety of composition, structure, color, and form, which distinguish- 

 es rocks of more modern growth. But* in dignity of massive strength 

 it stands altogether unrivaled. From the headlands of the Hebrides 

 to the far fiords of Arctic Norway it rises up grim and defiant of the 

 elements. Its veins of quartz, feldspar, and hornblende project from 

 every boss and crag like the twisted and knotted sinews of a magnifi- 

 cent torso. Well does the old gneiss of the north deserve to have 

 been made the foundation-stone of a continent. 



Whether vegetation clothed this earliest prototype of Europe, and, 

 if so, what were its characters, are questions to which at present no 

 answer is possible. We know, however, that the shallow sea which 

 spread from the Atlantic southward and eastward over most of Europe 

 was tenanted by an abundant and characteristic series of invertebrate 

 animals trilobites, graptolites, cystideans, brachiopods, and cephalo- 

 pods, 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 sediment constantly poured into it 

 from the northwest filled it up about as fast as the bottom subsided. 

 This slow subterranean movement was varied by uprisings here and 

 there, 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 inclosed basins, gradually cut off from the sea, like the 

 modern Caspian and the 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, Calamite, etc. the 

 oldest terrestrial flora yet known in Europe. The sea, dotted with 

 numerous islands, appears to have covered most of the heart of the 

 continent. 



