1889.] Geology and Palceontology. 493 
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 affect the lake valleys, as the glaciation of the 
surface rocks shows the movement to have been at angles 
(from 15^ to 90*^) to the trend 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 warping of the earth's surface in the lake region 
since the beach episode, after the deposit of the drift proper, 
is nearly enough to account for all rocky barriers which ob- 
struct the old valley and form lake basins. 
Establishment and dismembermetit of Lake Warren. This is 
the first chapter in the history of the Great Lakes, and is sub- 
sequent to the deposit of the upper boulder clay, and there- 
fore the lakes are all very new in point of geological time. 
By the warping movements 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 Cana- 
dian highlands northward of the Great Lakes. During the 
subsequent elevations of the continent beaches were made 
around the rising islands. Thus, between Lakes Erie, Huron 
and Ontario a true beach was formed at 1,690 feet above the 
sea around a small island rising 30 feet higher. With the 
rising of the continent, Lake (or perhaps Gulf of) Warren — a 
name given to the sheet of water covering the basin of all the 
Gfeat Lakes — was formed. A succession of beaches of this 
lake have been worked out in Canada, and from Lake Michi- 
gan to New York, extending over many hundreds— almost 
thousands— of miles. Everywhere the differential uplift has 
increased from almost zero, about the western end of the 
Erie basin, to three, five, and, in the higher beaches, more 
feet per mile. With the successive elevations of the land this 
lake became dismembered, as described in the succeeding 
papers, 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 glacial dams 
would be required. 
Discovery of the outlet of Huron- Michigan-Superior Lake 
into Lake Ontario, by the Trent Valley. With the contmental 
elevation described in the last paper— owing to the land ris- 
ing more rapidly to the northeast— Lake Warren became 
