242 THE HORSE AND ITS RELATIVES 



and realise that the great mountain systems of 

 the Pyrenees, the Alps, and the Himalayas were 

 still unborn, level surfaces in fact, partly washed by 

 the sea. The birth of the Pyrenees was at the 

 beginning of the Oligocene. At this time Switzer- 

 land was still a comparatively level plain, and not 

 until the close of the Oligocene did the mighty 

 system of the Swiss Alps begin to rise. Central 

 Asia was even yet a plain and upland, and only 

 during the Miocene did the Himalayas, the noblest 

 existing mountain chain, begin to rise to their present 

 fellowship with the sky. In North America, again, 

 since the close of the Eocene the region of the 

 present Grand Canon of the Colorado has been 

 elevated 1 1 ,000 feet, and the river has carved its 

 mighty canon through the rock to its present maxi- 

 mum depth of 6500 feet. 



" Those who have been impressed with a sense 

 of the antiquity of these wonders of the world, and 

 will imagine the vast changes in the history of 

 continental geography and continental life which 

 were involved, will be ready to concede that the 

 Age of Mammals alone represents an almost incon- 

 ceivable period of time." 



Admirably as is this aspect of the subject ex- 

 pressed by Professor Osborn, the force of the com- 

 parison would have been intensified if it had been 

 mentioned that at the time when the fox-like 

 Hyracothe^dum was wandering in the marshes of 



