THE OLD AGE OF CONTINENTS. 127 



have settled down some thousands of feet. . Their huge, 

 protruding folds, plaited together in comj^act array, have 

 been planed down to their innermost core; and from the 

 chips have been produced the lowlands of the south At- 

 lantic border, like the waterfront raised in a modern 

 city by carting down the sand-hills in the rear. The very 

 coal-beds interwoven in their stony structure are but the 

 fossilized swamps of an ancient continental surface that 

 has disappeared, clothed once by forest trees whose fam- 

 ily types have dropped from the ranks of existence, and 

 populated by those strange amphibians, half fish, half rep- 

 tile, which, like the fabled Colossus, bridged the chasm 

 between two dominions. 



There was a long and mediaeval time in American 

 history of which our records are mostly lost. The coal 

 lands had been finished; the atmosphere had been purged; 

 the Appalachians had been raised, and from their bases 

 stretched westward beyond the destined valley of the Mis- 

 sissippi an undulating upland but lately redeemed from 

 the dominion of interminable bogs. The western border 

 of this land skirted a mediterranean sea throucrli which, 

 probably, the Gulf Stream coursed, in certain cycjes, at 

 least, from the tropics to the frozen ocean. Here was 

 accumulated a soil; here descended genial rains; here 

 flourished tropical plants, and here wound majestic riv- 

 ers, fed by their hundreds of tributary streams. All traces 

 of this continental surface have disappeared. Terrestrial 

 animals must have populated the spacious forests; insects 

 uttered their sleepy hum amid the luxuriant foliage of 

 evergreen conifers; sluggish Labyrinthodonts crawled from 

 beneath the shade of perennial Cycads, and mailed and 

 armored fishes fought against the invasion of more modern 



