12 NEW YORK STATE MUSEUM 



of the ice front rested in the Genesee depression east of Leroy when 

 the earliest ice border drainage occurred, but that the lobation had 

 disappeared when the later channels, leading east toward Scotts- 

 ville, were made. 



All these glacial channels end in the Genesee valley at about 600 

 feet altitude where they built a series of broad deltas, extending 

 from Fowlerville north to Scottsville through a distance of 12 

 miles [pi. 7-9]. The control of the water level in the valley was 

 exercised by the channels which carried the lake waters out of the 

 valley and which will be described in the next chapter. 



Four lines of railway traverse the channel district from east to 

 west, taking advantage of the level stretches on the limestone pre- 

 pared by the ancient rivers. All these features are fairly shown 

 on the map. but a few special features require verbal description. 



The morainal or marginal drift of the ice sheet is too scanty to 

 represent on the map. There are two reasons for this; first, that 

 the rock rubbish carried by the ice was largely gathered into the 

 drumlin masses, as shown in the upper part of the map. plate 2; 

 second, that the vigorous river work at the retreating ice margin 

 swept the morainal drift eastward into the deltas. Over exten- 

 sive areas the limestone is practically bare. 



The axial directions of the drumlins should be noted. The 

 drumlins south of the parallel of Scottsville have a general north 

 and south attitude, or even northwest by southeast in the vicinity 

 of Linwood, in conformation to the valley slope, produced by the 

 southward flow of the ice lobe in the valley; while the northern 

 drumlins have a northeast by southwest direction, the prevailing 

 direction of all the ice-molded drift on the Ontario plain west of 

 the Genesee valley. 



The most singular feature of the district relates to the limestone 

 rock. It will be noted that on the map in the belt traversed by the 

 three east and west railways the channels are not definitely bounded 

 or limited. This is not from lack of knowledge of the district nor 

 because the channels are doubtful. There is no lack of evidence 

 of vigorous stream work, for all the drift has been removed and the 

 limestone eroded. But the rock strata has been so disturbed and 

 the surfaces tilted since the rivers did their work that the con- 

 tinuity of the channels and their walls is largely obscured. The 

 surface of the limestone is thrown into a large number of low but 

 conspicuous ridges and shallow basins due to settling or sinking of 

 the strata. These features were noted in 1S91 by G. K. Gilbert and 



