18 CHICAGO ACADEMY OF SCIENCES. 



above the district lying on its inner or iceward border, since that 

 district was filled with drift nearly to the level of its crest. But on 

 the outer, or landward, border there is usually a relief of 75 to 100 

 feet or more. Viewed from the outer border, the moraine in places 

 presents the appearance of a blufif or escarpment, though the rise 

 of 75 to 100 feet usually occupies a mile -or more. 



By reference to the map, it will be seen that there is a feeble 

 morainic belt lying a few miles back from the border of this drift 

 sheet. This is included with the Shelbyville system. It seems to 

 mark a brief halt of the ice sheet soon after it began its retreat. 



The main moraine, though very bulky, has but httle surface 

 expression, much of it being nearly as smoofh as the plains to the 

 north. It consists mainly of a single ridge, but in Edgar and 

 Coles Counties it has in places a double ridge. The feeble belt just 

 referred to presents in places a sharper morainic expression than 

 the main moraine, there being clusters of sharp knolls rising 

 abuptly thirty to fifty feet, or more, above border tracts. The 

 greater part of this belt, however, 'has a gently undulating surface, 

 like that of the main moraine. 



This sheet of drift, terminated by the Shelbyville moraine, is 

 compOiSed in the main of a soft, fresh -looking, blue till, markedly 

 in contrast with the partially cemented bro^vn and gray tills which 

 underlie it, and extend southward into the outlying districts. It 

 has long been recognized by well-drillers as a sheet very distinct 

 from the underlying tills. From the Shelbyville moraine a sheet 

 of soft blue till, similar to that in the moraine, is found beneath 

 plains, as well as moraines northward over much of Northeastern 

 Illinois. There appears to be but little difference in the structure 

 of drift in the morainic ridges from that in plane-surfaced tracts. 



Champaign Morainic System. — The Champaign morainic 

 system, though far less bulky, is fully as complex as the Shelbyville 

 system. It consists of several more or less distinct members sep- 

 arated by plains, the latter ranging in width from a mile or less up 

 to three and even five miles. It is exposed to view only in Eastern 

 Illinois, being combined with or overridden by the Bloomington 

 system from the vicinity of Bloomington westward. It is poorly 

 developed in Indiana, thoug^h small ridges are traceable across 

 Vermillion, Parke and Fountain Counties to Montgomei-y County, 

 Indiana, Where they are overridden by a morainic system of the 

 Late Wisconsin stage. The complexity of the system and the dis- 

 tribution of its several members may be seen by reference to the 

 accompanying map (Plate 2). - 



