EARLIER OPENING OF THE SAG OUTLET 241 



the Glenwood stage^ and that while the Des Plaines River from the nortli 

 was digging and deepening its channel on the west side of the moraine 

 and to the Sag and beyond, that the east side of the moraine was being 

 washed down and spread ont by wave action, as was the case all along the 

 west shore of Lake Michigan, for nearly a mile in width, until it was 

 washed down, and the 60-foot waters of Lake Chicago suddenly rushed 

 through into the deepened Des Plaines Channel, lowering the water level 

 to the 20-foot Tollestpn stage, when little or no water passed through the 

 narrow Sag Channel, afterward widened out by the long-continued deeper 

 flow of the Calumet stage. 



This is a plausible theory if it can be substantiated and proved by fur- 

 ther examination. In any event it seems quite evident that the water was 

 in some way lowered down quickly to the 20-foot Tolleston stage and 

 maintained there long enough for tlie formation of the peat beds that 

 have been referred to. 



Effects ov the Dtvebsion oi*' the Water in the (slactal Lakes in 

 THE Erie-Ontario Basin 



A natural explanation of the long-continued 40-foot water level pro- 

 ducing the second, or Calumet, terrace is found in the immense accession 

 of water to the south end of Lake Michigan from the glacial lake which 

 had been ponded in the Erie-Huron-Ontario Basin, which covered many 

 thousand square miles and was at first approximately 200 feet above the 

 present level of Lake Michigan. This body of water having its outlet at 

 first into the Ohio Basin through a v^ell defined channel at Fort Wayne, 

 Indiana, was lowered at successive stages as the ice receded northward. 

 First, there was a fall of approximately 50 feet when the Imlay outlet 

 across the thumb in Michigan was opened into the Grand River Valley, 

 and another 50 feet when the Ubly outlet farther north was opened by 

 the retreating ice, and, according to Mr. Taylor's estimates, another 20- 

 foot fall when the ice had receded beyond the thumb, letting the waters 

 of Lake Warren through Saginaw Bay into the Grand River Valley. 

 These three stages of water, named successively Lake Maumee, Lake 

 Whittlesey, and Lake Warren, are clearly marked by abandoned shore- 

 lines on the south side of Lake Erie. A beach 200 feet above Lake Erie 

 leads around to Fort Wayne, where it is interrupted by the channel of 

 the original outlet and resumed again on the other side. The 150-foot 

 beach leads around to the Imlay outlet and the 100-foot beach around to 

 the Ubly and Saginaw outlets. 



This would still leave an enlarging basin of water, covering many 

 thousand square miles, 70 feet above the Chicago outlet, continuing until 



