CHAPTER XI. 

 THE CHICAGO OUTLET AND BEACHES OF LAKE CHICAGO. 



PREVIOUS WRITERS. 



It is perhaps impossible to determine who was the first person to recog- 

 nize the evidence or form the conception of a sonthwestward outlet from the 

 Lake Michigan Basin to the Des Plaines Valley. Inquiry among the old 

 residents of this region shows that many of them recognized the beaches as 

 products of the lake, and they also noted that the lake once discharged into 

 the Des Plaines Valley. Evidently these conceptions were entertained for 

 many vears before any notice appeared in scientific publications. 



Bannister. — Probably the earliest scientific account of the outlet is that 

 given by Dr. H. M. Bannister, in 1868, in the Geology of Illinois. 1 How- 

 ever, a report by the U. S. Army Engineers upon the survey of the Illinois 

 Eiver, by Col. James H. Wilson and William Gooding, was published the 

 same year, which makes reference to the former southwestward discharge 

 of Lake Michigan. Dr. Bannister opens his discussion of the old lake outlet 

 and the raised beaches with the following statement : 



It is evident with a very little observation that, at a comparatively recent period, 

 subsequent to the Glacial epoch, a considerable portion of Cook County was under the 

 waters of Lake Michigan, which at that time found an outlet into the Mississippi 

 Valley through the present channel of the Des Plaines. 



Andrews. — One of the early publications of the Chicago Academy of 

 Sciences presents a discussion of the beaches by Dr. Edmund Andrews, 

 which has attracted wide notice. 2 The paper, however, deals mainly with 

 the work of the lake at its present stage. The ancient beaches are briefly 



' Geol. of Illinois, Vol. III. 1868. pp. 240-242. 



•The North American lakes considered as chronometers of post-Glacial time, by Dr. Edmund 

 Andrews : Trans. Chicago Academy of Sciences, Vol. II, 1870, article 1. pp. 1-24. 

 4 IS 



