COMPOSITE MORAIMO BELT OP .NORTHERN ILLINOIS. 305 



Fox River, and possibly it also includes a small part west of this stream. 

 It may extend as far west as the east border of English Prairie, at the State 

 line, and may embrace the tract between Fox Eiver and Crystal Lake 

 outlet, farther south. 



The equivalent of the Marseilles morainic system in this composite 

 belt is not satisfactorily determined. From northern Kendall County north- 

 ward it appears to have been overridden to some extent by a later advance 

 of the ice, and is perhaps completely concealed by the later deposits within 

 this composite belt. 



The portion of the composite belt east of Fox River has a width rang- 

 ing- from 6 or 7 miles at the State line to about 15 miles at the south line of 

 Lake and McHenry counties. Between these lines it is mainly in Lake 

 County, but includes a narrow strip in eastern McHenry County. From 

 the south line of these counties southward to Elgin it lies mainly in Cook 

 County, but includes the east border of northern Kane County and main- 

 tains a width of 14 to 15 miles. This is about the width of the Valparaiso 

 system farther south. 



GENERAL FEATURES. 



The general elevation of this portion of the composite belt is lower 

 than in the portion west of Fox River, being but little more than 800 feet 

 above tide. The highest points are found in southern Lake and northwest- 

 em Cook counties, and they rise but little above 900 feet. One of these, 

 just east of the village of Volo, stands 913 feet, and one in the northwest 

 comer section of Cook County 910 feet, as determined by the barometric 

 survey under Professor Rolfe. There are, however, but few other points 

 rising above 850 feet. 



There is a well-defined ridge-like crest standing 20 to 40 feet higher 

 than border tracts and having a width of about one-half mile which leads 

 southward with a somewhat winding course through western Lake and 

 northwestern Cook counties, forming the water parting between Fox and 

 Des Plaines rivers. East from this crest line there are only gentle swells, 

 seldom more than 15 feet in height, among which are occasional ponds and 

 small lakes. This district presents a slope which descends eastward at the 

 rate of 20 to 40 feet to the mile as far as the Des Plaines Valley. West 

 from the crest line the stnface is much more varied, there being tracts 



HON xxxviii 20 



