THE TOOTH OF TIME. 349 



know that an ancient river-bed stretches from Lake Michi- 

 gan down through the valley of the Illinois. The subter- 

 ranean explorations of the well-borer's auger have disclosed 

 multitudes of ancient gorges which are now filled up with 

 drift. If such tremendous gorges were ever cut, they were 

 filled up and obliterated by the great glacier. And may 

 not this reparation of the surface have been one of the be- 

 neficent operations of the glacier? We are told no glacial 

 action is detected west of the Rocky Mountains. Had the 

 great glacier been moved over the deep-cut gorges of the 

 great desert, they must have been filled and blotted out, 

 and the new-formed streams, on the advent of man, would 

 have been just in the act of surveying new channels for 

 themselves. The bare rock would have been clothed with 

 soil, and the " desert" might have been the garden of the 

 continent. 



