400 FIRST YEAR SCIENCE 



The effect of a submerged and eroded coastal plain is 

 seen in the Delaware and Chesapeake bay region. Here 

 the old river courses have been submerged, and the land be- 

 tween the rivers extends into the ocean in narrow, rather 

 flat strips with many little inlets along the sides. Easy 

 water communication is here possible to a considerable 

 distance inland and to almost every part of the land sur- 

 face near the coast. 



When the country was first settled, these water courses 

 were most advantageous to the settlers, as the produce of 

 the farms could be transported to sea-going ships with 

 comparatively little difficulty, much more easily than would 

 have been the case if it had been necessary to carry it by 

 land. There was little need of building roads, as each 

 farmer had a protected water highway to his door. Thus 

 a part of this region was known as " Tide-water Virginia." 



184. Lake Plains. Lakes which receive the drainage 

 from the land gradually have their floors smoothed over by 

 the sediment which the streams bring to them and the 

 waves and currents spread out. The lake itself is thus 

 filled, or in time the outlet wears back so as to drain 

 the lake. Thus a plain is left, the elevation of which is 

 determined by the elevation of the old lake bed. 



During the Glacial Period lakes were held in at some 

 places by huge dams of ice and at other places by accumu- 

 lations of sand or gravel brought down by the glaciers and 

 deposited so as to obstruct the valleys. The ice has now 

 disappeared and the gravelly material has often been easily 

 eroded, so that lake plains are not uncommon in the north- 

 ern United States. As the soil of these plains is fine and 

 easily cultivated, they furnish excellent farm lands. 



As already stated, a plain of this kind, remarkable for its 

 fertility and extent, is drained by the Red River of the 

 North and comprises the eastern part of North Dakota and 



