THE LAKE BOEDER MORAINIC SYSTEM. 405 



feet. Russell Station, situated on this plain near the State line, is 673 feet. 

 The plain between Middle and East ridges rises from 630 feet, opposite 

 Winnetka, to about 670 feet at the point where the ridges unite, 20 miles 

 north from Winnetka. 



In Indiana the border next the Valparaiso morainic system stands 50 

 to 70 feet above Lake Michigan, the lesser altitude being near the Illinois 

 line and the greater near the Michigan line. The plain between the Val- 

 paraiso moraine and the outer till ridge is but 2 to 3 miles wide in Porter 

 and Laporte counties; it however shows a descent toward Lake Michigan. 

 There is also a perceptible descent from the till ridge toward the lake. In 

 western Porter and in Lake counties the slope is apparently continuous 

 toward the lake from the border of the Valparaiso morainic system, no well- 

 defined till ridge being present. For a distance of 2 to 5 miles south from 

 the lake the sand deposits capping the till are heavy and their base is about 

 as low as the surface of Lake Michigan. 



In Berrien County, Michigan, the plain between the Valparaiso morainic 

 system and the outer till ridge stands 60 to 90 feet above Lake Michigan 

 and has a slight descent toward the lake. As it is but 2 to 4 miles in width, 

 the west border is only a few feet lower than the east. The plain between 

 the outer ridge and Covert Ridge stands 50 to 75 feet above Lake Michigan, 

 and also has a slight descent toward the lake. Its width in places is less 

 than a mile and nowhere exceeds 3 miles. 



In Van Buren and Allegan counties the lowland tract between the Val- 

 paraiso morainic system and Covert Ridg'e is less smooth than the southward 

 continuation in Berrien County. There are occasional ridges and knolls of 

 glacial drift ranging in height from 50 feet downward to 10 feet or less. 

 There are also numerous sandy ridges and knolls with a height ranging 

 from 30 feet downward to barely detectible waves in the surface. The 

 presence of the sand has tended to make the surface more uniform in eleva- 

 tion, since it is deeper in depressions than on the higher points. The plane- 

 surfaced part of the lowland stands usually 75 to 100 feet above Lake Michi- 

 gan, while the knolls occasionally reach a heig'ht of 150 feet or more above 

 the lake. This lowland tract presents greater oscillations in level in passing 

 from north to south than from west to east. It is generally somewhat lower 

 on the borders of the valleys than on the divides between them. If the 



