140 Geology of Upper Illinois. 
The construction of a canal-basin, at the termination of the ca- 
nal, with an area of five and a half acres, whose bottom is to be 
considerably elevated above the present level of the bottom-lands, 
serves to render this division of the undertaking also, very expen- 
sive. The cost of the entire canal, as estimated according to the 
report of the commissioners, is $8,654,337 ; but it is admitted that 
the estimate is too low, it being generally believed that the work 
will not be brought to a state of completion under ten millions 
of dollars. 
The geology of the chief portion of the route above described, 
is exceedingly simple and uniform, the great rock formation of 
the country being the magnesian limestone ; at least, this is the 
rock from the commencement of the canal, (four miles from Chi- 
cago, ) nearly to the mouth of the Kankakee. It also reappears 
west of the Fox river, as will presently be pointed out, and enjoys 
a wide distribution prebably throughout the whole of Upper Tili- 
nois and Wisconsin. A good opportunity for examining its char- 
acter occurs near Chicago, where the excavations have already 
been commenced. It here rises quite to the surface of the prairie. 
It is imperfectly stratified, with an evident dip of 10° or 15° to the 
north-west. Its color is light grayish white, with a frequent 
shade of yellow. It is compact in texture, and often slightly cel- 
lular or cavernous—a peculiarity which seems to be connected, 
for the most part, with the profusion of organic remains existing 
among its materials at the period of its formation. The follow- 
ing is a brief list of the fossils which fell under my observation 
at this locality: two species of Orthocera, a Turbo (one and a 
half inches in diameter) with a depressed spire; a large species 
of Pectunculus? ; a Terebratula, (with very prominent ribs, and 
but few in number ;) two species of Ammonites ; a Caryophyl- 
la, and a Favosites.* Some of the beds are wanting in fossils, 
and occasionally the rock puts on a shistose or slaty structure, in 
which case it forms a valuable flagging-stone, which is already 
employed to some extent in Chicago. 
The same rock reappears in the bed of the Des Plaines, twelve 
miles from Chicago, on the road to Juliet, as well as near the sui- 
<itSleteralof these: epecies Lam ee 
Rp, of Chicago. 
