146 SPARKS FROM A GEOLOGIST'S HAMMER. 



was the Niagara, as busy in Mesozoic time as to-day as 

 busy in Cenozoic time as if its work were just begun. 

 There is the living gorge, and there is the old gorge, 

 buried in its grave. Buried with materials obtained by 

 tearing to pieces some other land, buried by that agency 

 which piled up these hills of gravel and sand which 

 everywhere diversify the surface of our northern states; 

 which brought these acres of loose deposits from the 

 worn and wasted sides of northern hills ; which dipped 

 its flinty plow-share in the back of the surface rocks of 

 every northern state, and ripped up the rubbish which 

 has filled many an old river channel,, and plastered over 

 many an unsightly scar which the wear of time had cut 

 in the face of the land ; the same agency which scooped 

 out many of the lake basins, and scalped the hills for a 

 booty to bestow on a desolated and sorrow-stricken coun- 

 try. It was the continental glacier which did this work; 

 and the desolated country was a land that had been 

 weathered and worn by the erosions of unknown cycles 

 of time, a land gashed with the deep-cut gorges of long- 

 wearing streams; gullied by the summer torrents of many 

 geologic periods ; robbed of its slender soil by the pro- 

 longed denudations of the surface; a worn-out continental 

 expanse, a land exhausted in the service of the beasts 

 which had held dominion here through Cenozoic time, 

 but a land destined to receive a higher being, and now 

 renovated by such thorough-working agencies for his re- 

 ception. 



He who has visited the flourishing city of Nashville 

 finds it situated in the bottom of a basin, a great natural 

 basin, scooped in the rocks of central Tennessee, whose 

 sides are layers of Lower Silurian, Upper Silurian, De- 



