IX 
of Lake County, Indiana. It represents the drainage of the region, and by its 
division into townships and square miles, will enable the student to locate quite 
definitely, any phenomenon under consideration. The four townships in the 
northwest of Cook County, not represented on the map, are drained into Fox 
river, which runs nearly parallel to the Desplaines, and about twenty-five 
miles to the west of it. 
The location of the beaches as indicated by lines, to be described, is taken 
from Dr. Edmund Andrews; and the arrows indicating the direction of the striae 
on the rocks, are taken from Mr. Ossian Guthrie, a civil engineer of Chicago, 
who has had much observation in this vicinity. 
From north to south between the Desplaines river and the north and south 
branches of the Chicago river, runs the remarkably low divide between the basin 
of the Mississippi and that of the Great Lakes, or the St. Lawrence. This di- 
vide in its lowest part, is not more than twelve feet above the lake. It is so low 
that in times of high water, the Desplaines overflows the divide, and its sur- 
face waters run into Lake Michigan . 
The towns Eich and Bloom in the south part of the county, which do not ap- 
pear on the map, belong to the lake basin, and are drained northward into the 
Calumet. The northern portion of Lake County, Indiana, which is considered in 
the botanical area discussed, is also drained by the Grand Calumet. Near the 
south end of the lake are five small lakes lying in Cook County, and in Lake 
County, Indiana. The names of these lakes are, Calumet, Hyde, Wolf, Lake 
George and Berry Lake. These are connected by sluggish bayous with each 
other and with the Calumet river and Lake Michigan. The largest of these lakes 
is the Calumet, which is about three miles long. The greatest diameter of each of 
these five small lakes, is north and south, parallel to the greatest diameter of 
Lake Michigan itself. For the most part, the area outside of the lake basin has a 
black prairie soil with woodlands along the streams. Within the lake basin, 
there is a clay surface upon which are sand and gravel ridges covered with oaks, 
and between which are swamps and beds of peat. 
The mean altitude of Lake Michigan above mean tide at New York for 
thirty-five years is 581.28. f It is generally, however, placed at 582 feet. The 
Chicago datum which was fixed in 1847 is 1.65 feet below the mean altitude of 
the lake. Altitudes in the vicinity of Chicago are usually reckoned from this 
datum. The highest point of land within the city limits rises only twenty-five 
feet. The altitude of the general surface of the northern part of the county, 
may be inferred from the altitude of the four stations on the Chicago and 
Northwestern Eailroad given below. Glencoe, on the Milwaukee branch, on the 
lake shore near the northern line of the county, has an altitude of 93.7 feet. 
Lake Forest, eight miles northward, 122.8 feet. Palatine, on the Janesville 
branch, 170.6 feet, and Barrington, at the northern limit of the county, 249.9 
feet. The whole surface of the county rises northward. And again south of the 
city, it rises towards the southern margin of the county. The southern margin 
of the lake basin where the Wabash E. E. crosses it, has an altitude of 130 feet. 
The M. S. & L. S. E. E. crosses it at 260 feet, and the Illinois Central at 205 feet. 
But most of the land between the sand ridges lying south and east of Chicago 
around the small lakes and along the Calumet river, is but very little above the 
t See “Professional Papers” Corps of U. S. Engineers, No. 24, Comstock. 
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