CHAPTER YII. 



THE PEEMTAN AGE AND CLOSR OP THE PALJilOZOJC. 



The immense swamps and low forest-clad plains 

 wMcli occupied tlie continental areas of the Northern 

 Hemisphere, and which we now know extended also 

 into the regions south of the equator,, appear at the 

 close of the Carboniferous age to have again sunk 

 beneath the waves, or to have relapsed into the con- 

 dition of sand and gravel banks ; for a great thickness 

 of such deposits rests on the coal measures and con- 

 stitutes the upper coal formation, the upper "barren 

 measur^es^^ of the coal-miners. There is something 

 grand in the idea of this subsidence of a world of 

 animal and vegetable life beneath the waters. The 

 process was very slow, — so slow that at first vegetable 

 growth and deposition of silt kept pace with it ; and 

 this is the reason of the immense series of deposits, 

 in some places nearly 15,000 feet thick, which inclose 

 or rest upon the coal beds ; but at length it became 

 more rapid, so that forests and their inhabitants 

 perished, and the wild surf drifted sand and pebbles 

 over their former abodes. So the Carboniferous 

 world, like that of Noah, being overflowed with 

 water, perished. But it was not a wicked world 

 drowned for its sins, but merely an old and neces- 

 sarily preliminary system, which had fully served its 



