DESCRIPTION OP THE BEACHES 237 



from the Chicago Folio of the region south of the lake. All these beaches 

 are interrupted by the Chicago outlet along the line of the present drain- 

 age canal, this outlet having served its purpose during the formation of 

 them all. 



Peat Deposits between the Second and Third Beaches 



The facts most difficult of explanation connected with these beaches are 

 the accumulations of beds of peaty material underlying the second (Calu- 

 met) beach. These were noticed by Doctor Andrews at various places, 

 especially near Evanston, where they not only underlie the second beach, 

 but 



"extend eastward across the interval between it and tlie third beach. Its level 

 is no higher than that of the third beach, being only 12 to 15 feet above the 

 present level of Lake Michigan. . . . The peat is immediately overlaid by 

 about five feet of sand, above which there is a bed of coarse gravel. The 

 gravel is thin near the borders of the bar, but has a thickness of 10 or 12 feet 

 at the highest part. It is capped by a thin deposit of sand, and has also layers 

 of sand interbedded in its thickest parts. The presence of this gravel makes 

 it certain that the old marshy land surface has not been buried by the drift- 

 ing of material from the lower beach. There seems no escape from the con- 

 clusion that the lake stood at a lower stage than the level of the second beach 

 before that beach and the bar under discussion were formed." ^ 



Also, according to Leverett : ^ 



"For a few miles in the vicinity of the State line between Indiana and 

 Michigan there are exposures of peaty material along the bluff of Lake Mich- 

 igan at levels ranging from about 15 feet above the lake down to the water's 

 edge. . . . Near Michigan City peaty layers just above the water's edge are 

 nearly continuous for a distance of a mile or more and occur at frequent inter- 

 vals from Michigan City to the Michigan State line. Above the peaty beds 

 pebbly sand in places reaches an elevation of 30 feet above the lake, or nearly 

 to the level of the second beach. The peat appears, therefore, to have been 

 developed prior to the formation of that beach, and probably has the same age 

 as that noted near Evanston, Illinois." 



Later, however, in Monograph LIII, Mr. Leverett hesitates about ac- 

 cepting this evidence as conclusive. Speaking of the Evanston peat 

 deposits, he suggests that 



"a bar might be extended out over a peat deposit standing at the same level as 

 the lake and 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." * 



2 Leverett : Illinois glacial lobe, p. 445. 



3 Ibid., p. 445. 

 * Ibid., p. 356. 



