360 GEIKIE 



flora of which any abundant records have yet been found 

 in Europe. The sea, dotted with numerous islands, appears 

 to have covered most of the heart of the continent. 



A curious fact deserves to be noticed here. During the 

 convulsions by which the sediments of the Silurian sea-floor 

 were crumpled up, crystallised, and elevated into land, the 

 area of Russia seems to have remained nearly unaffected. 

 Not only so, but the same immunity from violent disturb- 

 ance has prevailed over that vast territory during all sub- 

 sequent geological periods. The Ural Mountains on the 

 east have again and again served as a line of relief, and 

 have been from time to time ridged up anew. The German 

 domains on the west have likewise suffered extreme con- 

 vulsion. But the wide intervening plateau of Russia has 

 apparently always maintained its flatness either as sea- 

 bottom or as terrestrial plains. As I have already remarked, 

 there has been a remarkable persistence alike in exposure 

 to and immunity from terrestrial disturbance. Areas that 

 lay along lines of weakness have suffered repeatedly in 

 successive geological revolutions, while tracts outside of 

 these regions of convulsion have simply moved gently up 

 or down without material plication or fracture. 



By the time of the coal growths, the aspect of the 

 European area had still further changed. It then consisted 

 of a series of low ridges or islands in the midst of a shallow 

 sea or of wide salt-water lagoons. A group of islands 

 occupied the site of some of the existing high grounds of 

 Britain. A long, irregular ridge ran across what is now 

 France from Brittany to the Mediterranean. The Spanish 

 peninsula stood as a detached island. The future Alps 

 rose as a long, low ridge, to the north of the eastern edge 

 of which lay another insular space, where now we find 

 the high grounds of Bavaria and Bohemia. The shallow 

 waters that wound among these scattered patches of land 

 were gradually silted up. Many of them became marshes, 

 crowded with a most luxuriant cryptogamic vegetation, 

 specially of lycopods and ferns, while the dry grounds 

 waved green with coniferous trees. By a slow intermittent 

 subsidence, islet after islet sank beneath the verdant 

 swamps. Each fresh depression submerged the rank 



