THE LAKE-BORDER MORA1NIO SYSTEM. 385 



At Senator C. B. Farwell's artesian well, in Lake Forest, rock is struck 

 at 160 feet. The well mouth is 40 to 45 feet below the crest of East Ridge 

 at Lake Forest and about 75 feet above Lake Michigan. 



At Highland Park rock is struck at 160 to 175 feet. The elevation 

 above the lake is 100 to 115 feet. 



At Lloyd's artesian well, in the north part of Winnetka, rock is struck 

 at 150 feet. The well mouth is by surveyors' level 78 feet above Lake 

 Michigan. 



At Ravenna a well strikes rock at 164 feet. The surface level has not 

 been accurately determined, but it is probably about 100 feet above Lake 

 Michigan. 



Near Schermerville rock is struck at 147 feet. The surface elevation 

 does not exceed 100 feet above Lake Michigan. 



On the crest of West Ridge, in sec. 14, Maine Township (T. 41, R. 

 12 E.), rock is struck at 110 feet. The elevation is probably about the 

 same amount above the lake. 



STRUCTURE OF THE DRIFT. 



Along the lake shore the bluffs from Winnetka to the vicinity of Wau- 

 kegan rise abruptly 75 to 90 feet and present many good exposures of the 

 drift to this depth. There is at the surface a pebbly yellow clay 8 to 13 

 feet in depth, which is similar to that in the other moraines. Beneath this 

 clay is a grayish blue till containing occasional sand pockets saturated with 

 water. These, however, form but a small part of the drift. The bulk of 

 the bluff is a compact till, but moderately pebbly and exposing only an 

 occasional embedded bowlder. It was noted that the pebbles and bowlders 

 are usually striated. 



Neither East Ridge nor West Ridge nor the northern portion of Mid- 

 dle Ridge has gravelly knolls of any consequence, but the southern portion 

 of Middle Ridge, lying in Cook County, has many such knolls. Indeed, 

 nearly every prominent knoll contains gravel. It seldom exceeds 15 feet 

 in depth and appears to be confined to the knolls, for they are situated on 

 a basement ridge of till similar to the till exposed along the lake bluff. 



But one complete reliable section of the drift could be obtained, which, 

 though valuable, needs to be supplemented by other records to furnish a 

 mon xxxvin 25 



