Bevieir of Recent Geological Literature. 817 
* 
glaciated regions, (b) That tlie glaciers are considered (by some) to 
erode, (c) Tlie supposed necessity, as the terrestrial warping was not 
known. 
In reply : Living glaciers abrade but do not erode hard rocks and both 
modern and extinct glaciers are known to have flowed over even loose 
moraines and gravels. Again, even although glaciers were capable of 
great plowing action, they did not ailect the lake valleys, as the glaciation 
of the surface rocks shows the movement to have been at angles (from 
15° to 90^) to the direction of the side of the vertical escarpments against 
which the movement occurred. Also the vertical faces of the escarpments 
are not smoothed off as are the faces of the Alpine valleys, down which 
the glaciers have passed. Lastly, the war pin i^' of the earth's surface in 
the lake region since the beach episode alter the deposit of the drift prop- 
er is sufficient to account for all rockj' barriers which may obstruct the 
basins . 
(3.) This is the first chapter in the history of the great lakes and is 
subsequent to the deposit of the upper boulder clay ; and therefore the 
lakes are all very new in point of geological time. By the movements 
of the warpings of the earth's crust, as shown in the beaches — after the 
deposit of the later boulder clay — the lake region was reduced to sea level 
and there were no Canadian highlands northward of the great lakes. Upon 
the subsequent elevation of the continent, beaches were made around 
the rising islands. Thus between lakes Erie, Huron and Ontario a true 
breach is formed at 1,690 feet above the sea, around a small island rising 
30 feet higher. With the rising of the land, barriers were brought 
up about this lake region, producing lake ( )r perhaps gulf of) 
Warren — a name given to the sheet of water covering the basin 
of all the great lakes. A succession of beaches of this lake has been par- 
tially worked out in Canada, Michigan, Ohio, Pennsylvania and New 
York, covering many hundreds — almost thousands — of miles. Every- 
where the differential uplift has increased from almost zero about the west- 
ern end of the Erie basin to three, five, and, in the higher beaches, to 
from five to nine feet per mile. With the successive elevations of the 
land this lake becomes dismembered, as described in the succeeding pa- 
pers — and the present lakes had their birth. The idea that these beaches 
in Ohio and Michigan were held in by glacial dams to the northward is 
disproven by the occurrence of open water and beaches to the north, which 
belong to the same series, and by the fact that outlets existed where placid 
dams are required. 
(4.) AVith the continental rise described in the last paper — owing to 
the land rising more rapidly to the nortlieast — lake Warren became dis - 
membered, an 1 Huron, Michigan and Superior formed one lake; the Erie 
basin really was lifted out of the bed of lake Warren and became drained, 
and Ontario remained a lake at a lower level. The outlet of the upper 
lake was south-east of Georgian bay by way of the Tr^nt valley into 
lake Ontario at about sixty miles west of the present outlet of this lake. 
The waters of this upper lake were 20 feet deep over this outlet into the 
Trent valley, and long continued to flow through a channel from one to 
