REPORT OF THE DIRECTOR I919 45 



continued. Where the equihbrium was estabh'shed across a 

 region of no great topographic irregularity, as in the central 

 west of the United States, the front of the ice would have 

 a relatively straight outline; but where the front, during a halt in 

 the melting, rested over a region of notable relief, as in any part of 

 the Appalachian plateau, it would be very irregular in outline for, 

 as during the advance, tongues of ice would project far southward 

 along the valley lines. This condition would in fact be much 

 accentuated during the retreat of the ice, as the ice erosion during 

 glacial occupation greatly enlarged these valleys in cross-section 

 and made them straight and continuous over long distances north 

 and south by obliterating the preglacial divides. Accordingly it may 

 be conceived that long narrow lobes of the ice extended southward 

 beyond the main front along such valley lines, while the hill countiy 

 between had been melted clear of ice. On the summits the ice was 

 thinner and also more stagnant, hence would disappear more rapidly 

 than in the deep troughs with their greater thickness of ice and 

 freer supply. 



The point to this somewhat lengthy statement of conditions at 

 the time of a halt of the ice, with reference to the Tully glacial 

 series, is that such an equilibrium occurred just there and, jointly 

 with the erosive action of the ice, was responsible for the phenomena 

 exhibited in this section. About a mile to the west of the village 

 of Tully and about a mile to the north there is encountered a very 

 steep slope in the floor of the southward continuation of the Onon- 

 daga valley, a descent of some 300 feet within a mile. This declivity 

 marks the inner side of a huge morainic accumulation made by a 

 lobe of ice that extended up to this point in the valley and rested 

 there for a long time. This declivity is not indicated very sharply 

 on the photograph of the relief model (plate i), but is a very marked 

 feature on the topographic map of the region, plate 2, on which it is 

 labeled " Tully moraine." It is shown graphically in the photo- 

 graph (plate 3) taken from a point on the inner side of the moraine 

 itself, just where the deposit joins the valley wall on the west side. 

 The gentler slope to the south is the front of this moraine, and the 

 wide flat plain with the lakes is the out wash accumulation that was 

 formed at the same time. 



References to the Tully Glacial Series in the Literature 



Having gained now a general acquaintance with the glacial history 

 of the region, it will be interesting to pause, before considering its 

 special phenomena, to note such references to the area as occur in 

 geological literature. 



