HISTORICAL REVIEW 3 



No differentiation is made by Bannister of the life of the different lake per- 

 iods; it is probable that the complicated stages of the glacial lakes, as under- 

 stood today, were not known or comprehended at this time. The section at 

 Evanston, quoted above, evidently includes strata referable to at least three 

 lake stages — Glenwood, Calumet, and Toleston. No. 8 of the section is refer- 

 able to the Calumet and Toleston stages; no. 7 is evidently post-Toleston; 

 1-6 are of Hammond age; the stratum of vegetable mould resting on the blue 

 clay probably represents the Bowmanville low water stage. 



1870. Andrews. 7 — Dr. Edmund Andrews, in discussing the ancient lake 

 beaches thus refers to a peat formation underlying the Calumet beach ridge: 

 " In fig. 4, 5 represents an ancient subaerial soil, which in many places becomes 

 a thin peat bed, with remains of grass still on its surface, which runs entirely 

 under the middle beach. " Dr. Andrews was apparently the first person to 

 suggest a Post-Glenwood low water stage. No mention is made by Dr. 

 Andrews of organic remains being found in this deposit. 



1888. leverett. 8 — In this paper Mr. Frank Leverett discusses with much 

 detail three ancient beaches, referring to the remains of life as follows : 



Glenwood or Upper Beach 



Section in Mr. Haas' gravel pit, Oak Park 



1. A brown-stained gravel at the surface extending down the slope. Depth, 18-30 inches. 



2. Fine gravel (unstained), 24 inches at top, increasing to 48 inches near base. 



3. Sand beginning with scarcely any thickness at the top, but increasing to a thickness of 36 

 inches at the base of the excavation. 



4. A bed of fine gravel increasing like no. 3 from 0-48 inches in thickness.. 



5. Fine gravel nearly four feet in thickness, which passes upward from near the east side of 

 the excavation, assuming a nearly horizontal position beneath the crest of the rjidge. 



6. Sand at the bottom of the excavation becoming thicker toward the higher part of the 

 ridge. Depth 6-36 inches. 



"Molluscan shells thought to be Unios, and smaller shells have been 

 found in no. 6, but none of these were at hand at the time of my visit. Mr. 

 Haas afterwards sent an oyster shell which was embedded in no. 6, and near 

 itwas the tooth of a mammoth. If the oyster shell has not been introduced 

 it suggests much as to a salt water lake. It is possible that the shells 

 thought by Mr. Haas to be Unios, were salt water mollusks. We learned 

 of no other instances of the occurrence of molluscan remains along the 

 upper beach." 



A personal examination of this gravel pit failed to reveal animal life of 

 any kind. The oyster shell was undoubtedly introduced artificially; there 

 is no evidence of a postglacial intrusion of the sea in this region. 



7 Trans. Chicago Acad. Sci., II, p. 15, 1870. 

 » Trans. Wis. Acad. Sci., Ill, pp. 177-188, 1888. 



