HISTORICAL REVIEW 19 



the presence of peat under the gravel suggests a lower stage of water it can 

 scarcely be said to prove it conclusively, for a bar might be extended out over 

 a peaty deposit standing at the same level as the lake and might press it down 

 and thus give it a lower level than it had while in process of growth. At the 

 Evanston locality this interpretation would seem very plausible, for the bar 

 was built out into water of considerable depth by southward moving currents. 

 Other peaty deposits are extensively covered by the gravels of the Calumet 

 beach along the bluff of Lake Michigan between Michigan City, Ind., and New 

 Buffalo, Mich. In this place there seems to have been no bar, but a regular 

 beach. The peat ranges from about 15 feet above the lake down to the water's 

 edge. The layers, few of which are more than 6 inches thick, are interbedded 

 with sand. One layer standing 12 to 15 feet above the lake is traceable con- 

 tinuously for fully half a mile along the shore about 2 miles southwest of New 

 Buffalo. Near Michigan City the peaty layers are continuous just above the 

 water's edge for a mile or more. Pebbly sand above the peaty beds in places 

 reaches an elevation of 30 feet or more above the lake or nearly to the level of 

 the Calumet beach. The sand evidently was deposited during the develop- 

 ment of that beach and the peat is certainly as old as the beach. The beach 

 may have been extended out over a peaty deposit, as was suggested in the case 

 of the Evanston deposits, but the conditions on the whole do not strongly favor 

 this view. If a lower lake level preceded the development of the Calumet 

 beach other evidence than that from the buried peat deposits should be found. 

 For instance, the valleys which entered the lake at this lower stage should have 

 been cut to a level below the Calumet beach and then the beach should have 

 been built across the beds of these channels as the Whittlesey beach was across 

 the valleys that were cut to the level of Lake Arkona in eastern Michigan. " 



Of the Algonquin beach Leverett says, 32 "The Algonquin beach carries in 

 a few places molluscan shells, and this beach of Lake Chicago is in places 

 richly supplied with these shells. In this respect it contrasts with the Calumet 

 and Glenwood beaches, from which molluscan remains have as yet been 

 reported at but one locality, near Bowmanville, north of Chicago. Sea shells 

 found by Alden and an oyster shell found by the writer may have been brought 

 in by human agencies." 



Leverett questions the interpretation of the writer, in placing the peaty 

 deposits of the Chicago region in a stage preceding the formation of the Calu- 

 met beach. The data for such interpretation are presented in the following 

 chapter. 



1916. sudworth 33 mentions the occurrence of spruce in the postglacial 

 deposits of Chicago, the reference being from Dr. Berry, to whom material 

 was sent by the writer. "Cones of both Picea canadensis and P. marina, the 



32 Op. tit., p. 357. 



33 Bull. 327, U. S. Dept. Agric, p. 3, 1916. 



