34 PHYSICAL GEOGEAPHY. 



given, the greatest of these would be so slight that it could 

 not be distinguished by the eye from a perfect level. It will 

 be seen, therefore, that there is a good degree of propriety in 

 regarding the whole State as a part of a great plain, the 

 lowest point of which within its borders, the south-eastern 

 corner of the State, is only 444 feet above the level of the sea. 

 The average height of the whole State above the level of the 

 sea is not far from 800 feet, although it is more than a thou- 

 sand miles inland from the nearest sea coast. 



The foregoing remarks are of course to be understood as 

 applying to the surface of the State as a whole, taking a 

 general view of it; but when we come to consider its surface 

 features in detail we find a very interesting diversity, and 

 even much romantic beauty in some parts. Nearly all this 

 diversity of surface, however, has been produced by the for- 

 mation of the valleys out of the general level, as will be 

 explained on following pages, under the heads of Rivers and 

 Surface Deposits. 



The general level that has just been assumed for the State 

 has even now to some degree a real existence, for we are 

 usually able to detect in all parts of it a general upper 

 level of surface between all the streams, down from which the 

 valleys of those streams have been eroded by the action of 

 their own waters during the unnumbered years of the Terrace 

 epoch. This character of surface is strikingly seen in the 

 southern part of the State, where the upper surface, usually 

 prairie, often presents to the eye a well marked level line 

 upon the horizon as seen in the distance. In the northern 

 part of the State, however, the surface has from the begin- 

 ning been more undulatory, but this subject will be again 

 referred to under the head of Drift Deposit and elsewhere in 

 the report. 



It is in the northeastern part of the State that the river 

 valleys are deepest ; consequently, the country has there 

 the greatest diversity of surface, and its physical features are 

 most strongly marked. In all parts there is a pleasing 

 diversity of surface, which becomes much increased in 



