532 Professor Herman Le Roy Fairchild — 



S. 45-60 W., and the drumlins are generally pointing soutb-west. 

 Ten miles east of Eochester the drumlins are due north and south, 

 and further away they veer to east of south. The depression of 

 Irondequoit bay and valley is the dividing-line. 



At the last recessional phase the ice over Eochester was given 

 a southward and spreading movement, due probably to a re-entrant 

 angle in the ice-body over the Irondequoit depression, where the 

 ice was more rapidly removed by the deep glacial waters. This 

 produced the crescentric moraine with which the Pinnacle Hills 

 are correlated.^ 



Thickness of Ice-cap. 



If we locate the margin of the ice-sheet at the terminal moraine, 

 and assume the average slope of the surface to be 30 feet per 

 mile for over 100 miles from the margin, the elevation of the ice- 

 surface above tide-level is estimated as follows : over the eastern 

 end of Lake Erie, 2,800 feet ; at Buffalo, 3,000 feet ; at Eochester, 

 4,000 feet ; at the centre of Lake Ontario, 5,000 feet ; at Syracuse, 

 5,500 feet ; over the middle of Seneca Lake, 4,200 feet. 



The thickness of the ice over the same localities is estimated, 

 taking account of land altitude, and making allowance of three feet 

 per mile for north-eastward differential uplift, as follows: over 

 the eastern end of Lake Erie, 2,300 feet ; at Buffalo, 2,400 feet ; 

 at Eochester, 3,700 feet ; at the centre of Lake Ontario, 5,700 feet ; 

 at Syracuse, 5,400 feet ; over the middle of Seneca Lake, 4,600 feet. 



Glacial Deposits. 

 General Drift Sheet. 



On account of the variety, in kind and resistance, of the subjacent 

 rock strata, the Glacial Drift is very variable in both amount and 

 composition. It is usually thin upon the outcrop of hard strata, and 

 in any locality consists largely of material derived from rocks lying 

 immediately northward. For the bulk of material the distance of 

 transportation is not great. 



Drutnlins. 



This area includes some most remarkable groups of drumlins. 

 Over some districts the gi'eat bulk of drift seems to be gathered 

 into drumlin forms. The district between Eochester and Syracuse 

 is especially noticeable, as here the drumlins are more conspicuous, 

 rising abruptly from a level silt plain. In some places the drumlins 

 coalesce into great and elevated masses, as for example the " Turk 

 Hill" group, 12 miles south-east of Eochester. The typical form 

 of the region is not the short, mound-like or ovoid form, although 

 these are present, but much elongated or attenuated forms. A length 

 of one mile is common. They seem to have the boldest forms and 

 are more typical whore containing more adhesive or clayey material, 

 as along the belt of soft Salina shales. They are strangely wanting 



^ H. L. Fairchild, "The Kame Moraine at Eochester, New York" : American 

 Geologist, vol. xvi, pp. 39-51. ! 



