508 The American Naturalist. [June, 
GEOLOGY AND PALEONTOLOGY. 
Continuity of the Glacial Epoch.—The question of Pre-glacial 
or Inier-glacial erosion of the rocky gorge of the Ohio River and its 
tributaries is made the subject of a paper by Rev. G. Frederick 
Wright inthe Am. Journ. Sci., March, 1894. The writer, as it is well 
known, maintains the former theory, and gives the following summary 
of the course of events connected with the Glacial period, stating 
more fully than has heretofore been done how those who question the 
long interglacial epoch can account for what has been called the 
moraine of the second Glacial epoch, and for the river terraces which 
everywhere, east of the Mississippi River, head near the moraine 
“Ist. The earlier portions of the Tertiary period were characterized, 
throughout all the northern hemisphere, by low altitude of land and a 
warm temperature even in close proximity to the pole.” 
“2d. A period of slow continental elevations of the regions which 
are now covered by Glacial drift, extending through some hundreds 
of thousands of years, was in progress late in the pliocene epoch. 
During this stage of events, the fiords which characterize the northern 
portions of both Europe and America, and the extensive rock gorges, 
like those of the upper Ohio River and its tributaries, were eroded.” 
“3d. Contemporaneously with this continental elevation at its max” 
imum stage, and chiefly as a consequence of it, Glacial conditions 
characterized all the higher latitudes of North America and Western 
Europe. In eastern North America, the center of Glacial radiation 
was in the vicinity of James Bay. A land elevation of three or four 
thousand feet would perhaps have been sufficient to produce the Gla- 
cial conditions; but the accumulation of the Glacial ice would event- 
ually raise the surface several thousand feet higher.” 
“4th. Before the climax of the Glacial period, and perhaps in con- 
sequence of its burden of ice, the glaciated area began to sink until 
the land was, north of the Great Lakes at any rate, several hundred 
feet, at least, lower than it is now. But for some time after the begin- 
ning of the subsidence of the land, the rate of accumulation of ice 
would be greater than that of the subsidence, so that the general level 
of the glacier continued to rise. Thus the maximum extension of the 
ice field was actually reached but a short time before the decline of the 
period set in.” 
