1875.) Niagara. 137 
information is contained in the well-known works of Prof. 
Dana, not only in his admirable “‘ Manual of Geology,” 
but in various memoirs, amongst which I may especially 
mention his ‘‘ Geology of the Newhaven Region,” published in 
the “‘ Transactions of the Conneticut Academy”’ in 1870. I 
may mention, that with the exception of Dr. Dawson, of 
Montreal, the whole of the most eminent of the geologists 
of eastern North America are now agreed that the prin- 
cipal glaciation of America was effected by land-ice, though 
there is abundant proofs, as I shall have occasion to show in 
this paper, that at a later stage, boulders were scattered 
over the country by floating icebergs. That later stage of 
floating ice was due, however, I contend, both in America 
and Europe, not tou a submergence of the land below the 
ocean, but to the production of immense lakes of fresh 
water, by the damming up of the drainage of the 
continents by ice that flowed principally down the ocean 
depressions. In this conclusion, I have as yet no 
supporters amongst the geologists, either of America or 
Europe, if, indeed, I may not except Professor Hall, who 
informed me, in conversation, and authorised me to publish 
his opinion that the sea has never encroached on south- 
eastern New England since the deposition of the ‘‘f//,” and 
that the terraces of the Hudson and Connecticut were pro- 
duced by the blockage of their waters by ice that flowed 
down the ocean bed, and of the presence of which we have 
proof in the immense moraines that compose the whole of 
Cape Cod. 
GLACIAL PHENOMENA. 
The rocks through which the gorge of Niagara is cut are 
limestones, sandstones, and shales. ‘These rocks are all 
rounded and smoothed, and the limestones are frequently 
scratched and grooved. Besides the coarser ice marking, 
the rounded and smoothed surfaces of rock, when examined 
closely, exhibit innumerable fine scratches, which have been 
ascribed by Hall to small particles of sand imbedded in the 
ice that moulded the rocks, and he has shown the improba- 
bility that this moulding and fine scratching, which is uni- 
versal over the whole northern part of the State of New 
York, wherever the rocks are of sufficient hardness to re- 
ceive and retain striz, could have been effected by icebergs. 
Lying on these glaciated rocks are superticial deposits of 
drift, containing beds of unstratified clay, with boulders, 
sands, and loam. These are spread over the whole district 
like a mantle, so that natural exposures of the bed rock are 
rare, excepting in the gorges cut by the river. 
