RESURRECTION OF THE CONTINENT. 235 



Now in time of drought, when the immediate surface has 

 become parched, moisture rises by capillary attraction from 

 the nearest subterranean reservoir. Evidently the nearer 

 this reservoir to the surface, the more easily and rapidly 

 its alleviating effects will reach the suffering roots of veg- 

 etation. So far as I can perceive, the soils of regions cir- 

 cumstanced as I have supposed must be doomed to irreme- 

 diable sterility. 



The epoch of the last emergence of the land was the time 

 when the precise drainage features of modern times were 

 determined. The great undulations of the surface which 

 determine the principal water-sheds depend, it is true, upon 

 the conformation of the rocky crust, and probably existed 

 nearly as they now exist in the age anterior to the reign 

 of ice. But all the subordinate details of the drainage 

 were executed while the continent was rising from its last 

 ablution. There was a time when the descent of the Mis- 

 sissippi was so gradual that the waters spread out many 

 miles, and, like a vast bayou, filled the valley between the 

 bluffs which bound to-day its alluvial bottom. This is the 

 condition of the Amazon in the existing epoch. As the in- 

 terior of the continent became more elevated, the currents 

 of the rivers became swifter and narrower. Many river- 

 channels, obliterated by the agency of the glacier, and, far- 

 ther, by the blending and leveling of the submerging waves, 

 could not again be found when the continent was restored. 

 The new -formed streams were obliged to seek out new 

 paths, and dig new outlets to the sea. The ancient gorge 

 of the Niagara had been obliterated, and, when the labors 

 of that stream were resumed, a slight change in the config- 

 uration of the surface turned the current from " the whirl- 

 pool" farther to the east than before. On reaching, near 

 Lewiston, the brow of the escarpment which then formed 

 the head of the great Laurentian estuary, it missed its an- 



