332 THE ILLINOIS GLACIAL LOBE. 



County line, and thence westward down a similar grade to where it dies out 

 near Kentland (Purdue). The long ridge a few miles to the north appar- 

 ently holds a nearly uniform elevation about 680 or 685 feet above tide. 

 As indicated in the topographic map, PI. Ill, much of the area east of the 

 State line stands above 700 feet. It should also be noted that in the midst 

 of the sandy area the altitude is about as great as on the borders. 



SURFACE CONTOURS. 



The greater part of the sand-covered area has a nearly plane surface. 

 The Kankakee marsh, with an area of nearly 1,000 square miles, is very 

 Hat. while the portion north of the marsh has scarcely any ridges worthy 

 of note. In southeastern Pulaski and northern White counties, Indiana, 

 the surface is mainly level and level tracts are quite extensive in southern 

 Jasper County. In Illinois the surface is mainly plane, except on the outer 

 face of the Iroquois moraine and in a belt a few miles wide which follows 

 the south border of the Kankakee River, in both of which places there are 

 ridges and dunes of some prominence. 



The ridged portions of the sand in Indiana occupy southeastern Stark, 

 much of Pulaski, and the central portions of Jasper and Newton counties, 

 all of which lie southeast of the Kankakee marsh, as well as a narrow strip 

 on the east and south borders of the sand area in Fulton, Cass, White, and 

 Jasper counties. There are also scattering ridg-es in the midst of this level 

 portions of the sand area in that State. 



The most prominent ridges are 35 or 40 feet in height, but the majority 

 are less than 20 feet, and many are only 5 or 10 feet. The individual 

 ridges vary in breadth from 50 feet or less up to nearly one-eighth mile, 

 but are usually about 200 to 300 feet. Among the ridges, even where most 

 prominent, there are narrow strips with nearly plane surface. 



The prevailing trend of the ridges is usually easy to determine, though 

 in places the ridges wind about and interlock, forming an intricate network. 

 Those on the east border, in Pulaski County, Indiana, show a tendency to 

 a north-to-south trend, while those on the south border in Cass, White, and 

 Jasper counties, trend nearly east to west. Those on the south border of 

 the Kankakee trend about with the course of the stream, south of west in 

 the Indiana portion and north of west in the Illinois portion. Between the 

 ridges borderino- the Kankakee in Indiana, and those on the south and east 



