426 GLACIAL FORMATIONS OF ERIE AND OHIO BASINS. 



INNER BORDER PHENOMENA. 

 GENERAL FEATURES. 



The district here discussed as the inner border tract embraces the 

 portion of the Scioto Basin lying between the inner member of" the main 

 morainic system and the Powell moraine, which crosses the basin a few 

 miles north of Col^^mbus. The main pai't lies south of a line passing east 

 to west about 10 miles north of Columbus, though narrow projections 

 toward the north occur near both the east and the west border of the 

 Scioto Basin, as indicated on PI. XIII. 



This district has lower altitude than border districts. Its lowest part 

 is along the Scioto River, there being a gradual rise from the river, both 

 east and west, to the moraine just described. There is a southward descent 

 along the sides of the Scioto Basin as well as along the stream. The 

 altitude of the river bluff at the border of the Powell moraine north of 

 Columbus is about 876 feet, at Columbus 800 feet, and at Circleville 720 

 feet. The east and west borders of the basin are about 300 feet higher 

 than the axis followed by the river, and descend southward at about the 

 same rate. 



WEAK MORAINES. 



The greater part of this district presents a very smooth surface, and 

 portions of it west and southwest of Columbus are known as "the plains." 

 A few quite conspicuous knolls were formed, however, on the east side of 

 the river, and may indicate the position of the ice margin at a stage of 

 halting during the retreat. The position of the larger of these knolls and 

 ridges is indicated on PI. XIII. A conspicuous group known as the Spangler 

 Hills is found on the east side of the Scioto, about 8 miles south of Columbus. 

 As indicated by the East Columbus topographic sheet, there are, two points 

 that rise nearly 100 feet above the border plain. Small knolls appear near 

 this prominent group in a belt about 2 miles long from north to south, and 

 about a half mile in width. They are often sharp and conical, but associ- 

 ated Avith them are ridges which are more or less winding. The sharpest 

 knolls are gravelly, while those with the gentler slopes contain till. From 

 the north end of this belt northward a mile or more there are low swells 

 inclosing basins 8 or 10 feet in depth. In some cases the basins cover 

 several acres. This gently undulating tract carries a slight coating of till, 

 perhaps 10 feet in thickness, below which there is gravel. The next knoll 



