The Kame-Mornine at Rochester, y. Y. — FairchUd. 47 
plicable as the result of the concentration of the torrential 
waters in one channel. This objection may be answered by 
a discussion of the peculiar conditions, and a description of 
other kame areas of the region. 
The total amount of stream detritus in these hills may not 
be so great, comparatively, but it shows to full advantage be- 
cause it lies conspicuously upon a plain, instead of filling de- 
pressions in an uneven surface. 
The Pinnacle hills are only a small portion of the enormous 
amount of water detritus which the glacial drainage has left 
over the Genesee and Irondequoit region. The objection 
above noted would apply to other deposits of even greater 
magnitude. In a recent journey through the Genesee valley 
professor Shaler noted the unusual and remarkable amount 
of water deposits, which even occur frequently upon the drum- 
linoids throughout Monroe county and adjacent territory. In 
explanation it should be noted that the strata outcropping 
north of Rochester are peculiarly adapted to supply the finer 
material. The Medina sandstone is over 1,000 feet thick and 
has been excavated to form the southern side of the basin of 
lake Ontario. It contributed by preglacial decay and glacial 
erosion the material for the sand and tlie greater proportion 
of the gravel and cobble of all the water deposits of this re- 
gion. The overlying Clinton shales and thin bedded lime- 
stones with shale partings, and the 80 feet of Niagara arena- 
ceous shale supplied the bulk of the silts. The Niagara lime- 
stone occurs in the drift chiefly as boulders. 
At the time of the formation of the Rochester moraine the 
Ontario glacier had probably become quite stagnant, and ab- 
lation of the surface had doubtless exposed the lower portion 
of the ice which was heavily charged with material from the 
Ontario excavation. The conditions thus favored the rapid 
accumulation of detritus, along certain portions of the ice 
front, by the heavy drainage from the rapidly dissolving ice. 
It is also suggested that the Warren waters had removed 
the thin edge of the ice sheet so rapidly by melting and flo- 
tation that little opportunity was given for local accumula- 
tion of any kind of glacial nuiterial over a belt several miles 
wide south of Rochester. When the balance between the ice- 
flow and the ice destruction was established for a short time 
