216 Frank Carney 



marked by beaches and other shore phenomena corresponding to, 

 but lower than, the original beach. 



With a further retreat of the ice a new outlet north of Imlay 

 was revealed, the Ubly channel; its altitude is about thirty feet 

 lower than the former. In consequence, the level of Lake Maumee 

 fell this amount. 



The Whittlesey stage. This lower lake is called Whittlesey, 

 after one of the early geologists of Ohio, Colonel Whittlesey, who 

 was connected with our first Survey, organized in 1836. During 

 the Whittlesey stage, a continuous sheet of water extended across 

 northern Ohio. This lake was at least 160 feet deeper than the 

 present Lake Erie. It drained across Michigan into glacial Lake 

 Chicago, the name used for the water in front of the Chicago ice 

 lobe. Lake Chicago overflowed through the course followed now 

 by the Chicago sewage canal, into the Illinois River, thence to the 

 Gulf. The Erie basin ice lobe, during, the Whittlesey stage, 

 blended eastward into the margin of the glacier extending across 

 western New York. Therefore, Lake Whittlesey reached from 

 the state of Michigan, on the west, to Central New York, on the 

 east. Its margin across Ohio is marked by a splendidly developed 

 shoreline, which I discuss in a later section. 



It is evident that Lake Whittlesey endured till the ice had with- 

 drawn from some divide in New York state lower than its overflow 

 in Michigan. The ultimate control of the western outlet, then, 

 was an altitude that might be revealed along the southern slope 

 of the Mohawk lowland. During the entire existence of this 

 lake stage, the ice sheet filled the Mohawk area, and abutted the 

 Catskill region south. It is very likely that before the close of the 

 Whittlesey stage, its waters flowed both to the east and west. 

 This condition would naturally follow when the ice sheet should 

 withdraw sufficiently down the southern wall of the Mohawk 

 valley to disclose a level not very much higher than the Ubly 

 outlet. With a slight difference in the level of two channels, a con- 

 tinuous west wind might cause an eastern overflow, temporarily 

 at least. Thus, for some time, Lake Whittlesey may have over- 

 flowed into the Atlantic by the two routes. When, however, the 

 ice had appreciably retreated in the Mohawk lowland, the level 

 of Lake Whittlesey was bound to fall correspondingly, and a new 

 outlet be permanently established. 



