WELLS OF LASALLB COUNTY, ILLINOIS. 635 



LASALLE COUNTY. 

 GENERAL STATEMENT. 



Lasalle County is situated in the north-central part of the State, imme- 

 diately east of Bureau and Putnam counties and above the bend of the 

 Illinois River. That river traverses the county nearly central from east to 

 west. It is the second county in size, being exceeded only by McLean 

 County, and has an area of 1,152 square miles. Ottawa, the county seat, 

 is situated near its geographic center, at the junction of Fox River with the 

 Illinois. Fox River traverses the northeastern portion in a southwestward 

 course and receives the drainage of much of the northern half of the 

 county. Vermilion River traverses the southern portion of the county in 

 a northwestward course, entering the Illinois opposite the city of Lasalle 

 and dividing the portion south of the Illinois into nearly equal parts. The 

 Little Vermilion drains the northwest portion of the county in a southward 

 course and enters the Illinois at Lasalle. 



The most elevated portion of the county is in the northwest corner, 

 which is occupied by the inner portion of the Bloomington morainic system. 

 The altitude here reaches about 900 feet above tide. Much of the uplands 

 in the county stand below 700 feet. The extreme southwestern portion, 

 however, rises to about 750 feet, and the Marseilles moraine on the eastern 

 border of the county has a crest line about 750 feet above tide. The 

 greater portion of the surface is nearly plane. There is, however, aside 

 from the two moraines just mentioned, a small morainic belt (Farm Ridge) 

 which occupies the upland immediately east of Little and Big Vermilion 

 rivers, crossing the Illinois River between Utica and Lasalle. 



The principal streams of the county have excavated valleys in the rock, 

 and wells on the uplands frequently enter rock at depths of 50 feet or less, 

 except in the elevated portions referred to in the northwest, southwest, and 

 east parts of the county. In the northwest part the thickness of the drift 

 exceeds 200 feet. In the southwest part it is apparently about 150 feet. In 

 the eastern part, along the Marseilles moraine, it is 200 feet or more. The 

 average distance to rock in 55 of the deep wells on the upland and 8 deep 

 wells in the valleys is 99 feet. Records were obtained of 85 other deep 

 wells which do not enter rock, though their average depth is 89 feet. They 

 are largely situated on the Marseilles moraine. The wells entering rock 



