§9. EPOCH OF TERRESTRIAL MAMMALTA. 135 



Human Epoch, that which forms the immediate subject 

 of investigation may be designated the Epoch of terrestrial 

 mammalia. 



" When the traveller," says Cuvier, " passes over those 

 fertile plains, where the peaceful waters preserve, by their 

 regular course, an abundant vegetation, and the soil of 

 which is crowded by an extensive population, and enriched 

 by flourishing cities, which are never disturbed but by the 

 ravages of war, or the oppression of despotism, he is not 

 inclined to believe that nature has also had her intestine 

 wars, and that the surface of the globe has been overthrown 

 by various revolutions and catastrophes. But his opinions 

 change as he penetrates into that soil at present so peace- 

 ful ; or as he ascends the hills which bound the plains. 

 His ideas expand, as it were, with the prospect ; and so 

 soon as he ascends the more elevated chains, or follows the 

 beds of those torrents which descend from their summits, 

 he begins to comprehend the extent and grandeur of the 

 physical events of ages long past. Or if he examines the 

 quarries on the sides of the hills, or the cliffs which form 

 the boundaries of the ocean, he there sees, in the displace- 

 ment and contortion of the strata, and in the layers of 

 water-worn materials, teeming with the remains of animals 

 and plants, proofs that those tranquil plains, those smooth 

 unbroken downs, have once been at the bottom of the deep, 

 and have been lifted up from the bosom of the waters ; and 

 everywhere he will find evidence that the sea and the land 

 have continually changed their place."* 



In almost every part of the world, beneath the modern 

 alluvial soil, extensive beds of gravel, clay, and loam, are 

 found spread over the plains, or on the flanks of the moun- 

 tain chains, or on the crests of ranges of low elevation ; and 

 in these accumulations of marine and fluviatile debris, are 



* " Discours sur les Revolutions de la Surface du Globe." 



