104 NEW YORK STATE MUSEUM 



but no other pronounced moraine is to be found in this region to 

 correspond with the moraines extending from Lockport to Can- 

 andaigua or from Medina to Irondequoit bay. It seems probable 

 therefore that, on the advance of the glacier to the Salina de- 

 pression, the frontal moraine was dropped into the valley, bring- 

 ing the level of the valley nearly to the level of the Niagara 

 escarpment and giving a gentle incline, over which the glacier 

 passed. 



On the retreat of the glacier, several glacial lakes covered this 

 region; and the general topography of this section is much like 

 that around Oakfield, the entire depression being dotted with 

 kames and drumlins. The absence of a moraine to correspond 

 with the one from Medina to Irondequoit bay is probably due to 

 the more rapid retreat of the ice at the eastern border, which 

 would tend to form a more scattered deposit. 



In a former paragTaph, the writer made the statement that 

 the drainage from this valley probably flowed into the Mohawk 

 Tiver; and, as the pr-esent drainage is toward Lake Ontario, this 

 opinion may appear far-fetched. The reasons for this supposition 

 are (1) that the level of this part of the Salina depression is 

 about 125 feet above Lake Ontario, and, if there were an old 

 channel, it would have been more likely that this would be left 

 open than that a new channel would be formed. (2) The glacial 

 debris is held in place by a ridge of Niagara limestone or the 

 Medina sandstone, and this ridge was much higher in preglacial 

 times. (3) The Rome channel is blocked up by glacial debris. Of 

 these three reasons, the second is the only one that needs explana- 

 tion and is possibly the most important. 



As has been previously stated, the deepest part of the Salina 

 channel is from Lyons to Rome and thence through the Mohawk 

 valley, and to this is due the difference in the altitude of the 

 Niagara escarpment in this section and the section west of 

 Rochester. The tendency of the glacier being to bring the country 

 to a level, it naturally follows that the erosive force would be 

 greater in this section, where a narrow transverse ridge was 

 placed between two deep valleys, than in the region west of 



