32 TWELFTH REPORT. 



the head of the Imhiy Outlet, Since the ice border was near by the 

 Imhiy Outlet and remote from the Fort Wavue Outlet the water surface" 

 may have been drawn up by ice attraction to a slightly higher level at 

 the Imlay Outlet. The amount of ice attraction must be deducted from 

 the 60 to 65 feet to show the actual differential uplift. Another qualify- 

 ing condition is found in the amount of peaty filling Avhicli each outlet 

 contains. The amount appears to be several feet greater in the Imlay 

 Outlet than in the Fort Wayne. It may be sufficient to counterbalance 

 the amount that would need to be subtracted because of ice attraction. 



With further recession of the ice border on the Thumb lower outlets 

 were found across it. one near Ubly, and a lower one still farther north, 

 and the Imlay Outlet was abandoned. 



LflAe Arkona. The iov^•est of the three outlets across the Thumb 

 is not now exposed to view because the ice readvanced and filled it. 

 This readvance raised the lake waters to the level of the next higher 

 or Ubly Outlet. The beaches of the lake formed at this lovrer stage 

 are, however, preserved at certain places just outside the moraine of re- 

 advance at lower levels than the beach that opens into the Ubly Outlet. 

 The name Lake Arkona is applied to this water body that preceded the 

 advance of the ice, and the features of this lake have been discussed by 

 Taylor in an earlier report of the Michigan Academy.^ Its full limits 

 on the north are not known, but it is supposed to have extended over 

 much of the Saginaw basin as well as the district east of the Thumb. 

 It appears also to have extended eastward into ^N^ew York beyond 

 Buffalo to the vicinity of Alden Avhere its beaches are preserved in a 

 protected situation back of a moraine, thus duplicating the features 

 noted on the Thumb. 



Lal-e Whiitlrsei/. The stage of the lake that accompanied the re- 

 advance of the ice and utilized the Ubly Outlet has been named Lake 

 Whittlesey. Its beach is the best defined of the whole series in the 

 Huron-Erie basin, and was traced through much of southern Michigan 

 some 70 years ago by Bela Hubbard. It was used as a highway or ridge 

 road in the earliest days of settlement and still continues in use ex- 

 tensively. It is conspicTious as far north as the latitude of Tort Huron 

 on the east slope of the Thumb from St. Clair county to Lenawee and 

 thence continues around the western and southern sides of Lake Erie 

 into western New York. (Fig. 5.) Its eastern terminus in Kcav York 

 as well as its northern terminus in Michigan is found at a moraine 

 that marks the contemporary ice border. 



The Ubly Outlet discharged to a small lake in the portion of the 

 Saginaw basin southwest of Saginaw Bay and thence through the Grand 

 Kiver outlet to Lake Chicago. 



The beach of Lake Whittlesey is horizontal from near Birmingham, 

 a few miles north of Detroit, around the western and southern sides of 

 Lake Erie to the vicinity of Ashtal)ula, Ohio, but north from Birming- 

 ham and east from Astabula it shows a marked rise resulting from 

 difterential uplift. At the Ubly Outlet its altitude is about 60 feet 

 higher than in the horizontal portion, and in western New York it 

 reaches an altitude about 150 feet above the horizontal i)ortion. 



Lake Worirn. With the recession of the ice border from the northern 



^Seventh Report, 1905, pp. 29-36. 



