Observations in the Region at the Head of Lake 



Michigan. 



By Jens Jensen, Chicago, Illinois. 



Generally speaking- the topography of the district under dis- 

 cussion in the following notes is level. Geologically the region 

 at the head of Lake Michigan consists of the following forma- 

 tions : 



First. — Alluvial Deposit. 



Second. — Glacial Drift. 



Third. — Mo rain. 



The Alluvial Formation consists of a series of sand ridges 

 that form sand dunes toward the northern part with interven- 

 ing spaces, still inundated or here and there raised up above the 

 Lake level by decaying vegetation. All of the dry lands are 

 covered with forest growth. 



The Glacial Drift, known to geologists as Lake Chicago, 

 but commonly termed "Prairie/' consists of a heavy blue clay, 

 and was entirely treeless before the arrival of the white man in 

 this section. Judging- by its name it is almost level, and has a 

 poor natural drainage. 



The Morain borders on Lake Michigan north of Chicago, 

 here known as "Lake Border Morain," and also borders the 

 "Prairie," or "Glacial Drift," described before. This forma- 

 tion consists of a yellow, pebbly clay, and was originally cov- 

 ered with forest growth, part of which still exists where the axe 

 has left it alone. 



The elevation over Lake Michigan of these three different 

 formations varies from a few feet to i8o feet, the Morain being 

 the highest, with the exception of a few sand dunes that per- 

 haps reach still a greater height, but which will not be con- 

 sidered here. 



From the foregoing description of the formation of the 

 lands at the head of Lake Michigan it at once becomes evident 

 that there exists a difference in the vegetation covering; these 



