386 REVIEWS 
this lake Mr. Leverett has given the name Lake Chicago. The stages 
in the history of this lake are as follows: f 
(az) Glenwood stage, the highest stage, when the level was sixty 
feet higher than Lake Michigan is now. During this stage the outlet 
was cut down twenty feet. 
(4) A stage of recession, when discharge through the Chicago out- 
let ceased and the water withdrew from the Chicago plain in part or 
entirely. During this stage deposits of peat accumulated. 
(c) Calumet stage, in which the water again discharged through the 
Chicago outlet at a level forty feet higher than the present level of 
Lake Michigan. During this stage the Calumet beach was formed over 
the peat deposits of the preceding stage. 
(z) The lowering of the outlet gradually reduced the level of the 
lake twenty feet when the Tolleston beach was formed. — 
(ec) A lower outlet was opened to the north and the lake fell below 
the level of the Chicago outlet. This closed the history of Lake 
Chicago and inaugurated that of Lake Michigan. Between the 
Tolleston beach and the shore of Lake Michigan there is an extensive 
series of sand and gravel ridges among which lie the small lakes 
mentioned above. 
Abundant evidence of fresh water life has been found in the 
deposits of the Tolleston stage of the lake, but not in the deposits of 
earlier stages. On the surface of the Calumet beach, however,.marine 
shells of southern species have been found, which may have been: 
introduced artificially. 
The bulletin is essentially a popularized version of the work of the 
United States Geological Survey and is a tribute to the value of its 
investigations. It is to be hoped that this bulletin will stimulate the 
publication of similar essays on local geography elsewhere. Interest 
ip geography is certainly increased by such publications. 
CHARLES EMERSON PEET. 
