156 H. L. FAIRCHILD 
conspicuous role. In the Irondequoit esker it is 50 to 75 per 
cent. of the whole mass. The kames contain somewhat less 
waste of the Medina, although the red color is usually pro- 
nounced even upon the highest summits. The Medina is the 
lowest terrane of the region, the top being only about 100 feet 
above Lake Ontario. In the Victor subaqueous kames, leaving 
the lofty Hopper range out of account, Medina gravel has been 
lifted towards 500 feet. Of this height not over 200 feet is due 
to the southward rise of the rock base, which leaves nearly 300 
feet of actual lifting of the gravel. The distance from the 
Victor hills to the nearest Medina exposure, at the head of the 
Irondequoit gorge, is 12 miles. Another example is more strik- 
ing. The Corniferous chert also occurs upon the tops of the 
Victor hills. The limestone is supposed to underlie the hills, 
but it cannot extend farther north at present than three or four 
miles. Within that distance the Corniferous has been lifted 
about 300 feet. Flotation by ice in lake waters might explain 
the presence Of imagments of ichert) on these) summits, pubithie 
Medina gravel which forms a constituent part of the hill sum- 
mits cannot be so accounted for. The overriding of the gravel 
deposits by the readvancing ice will probably account for the 
till upon the higher kame summits, as it will for the angular 
blocks of Niagara limestone upon the summit of the Pinnacle, 
and for the till on Cobb’s hill of the Rochester kame-moraine, 
but. the sareas phere sdescribedmoive: no evidence morsiexvensive 
burial under glacial ice. 
The summits of the Hopper ridge are about 250 feet above 
the upper lake terraces. It seems possible that some part of 
this remarkable elevation of the water drift upon this ridge may 
be due to a pushing by the ice in a slight readvance. The 
direction and form of this high ridge, however, are not entirely 
consonant with its being a pushed moraine. The interior struc- 
ture of the hills is unknown. This explanation, a pushing by 
the ice, applies in part to the Rochester kame-moraine. Possi- 
bly it may partially apply in the case of the Fort hill range 
lying immediately north of the Hopper range, but it would 
