124 
FOURTEENTH REPORT. 
Hartt and Agassiz at the Glacial epoch in the northern hemisphere. 
Hartt says (p. 572) “it would seem that the great movements just ante- 
cedent and posterior to the drift period in South America have corres- 
ponded with those of North America during the same period.” 
Figure 4 illustrates the three regions of elevation, followed by sub- 
sidence presumably Champlain in time, which have just been mentioned. 
It might include also Fairbanks’ conclusion that the rivers of the Cali- 
fornia coast form a separate line of evidence strongly corroborating 
the testimony of the submerged river channels in that region. It is true 
that Falconer seems to make the Antillean subsidence slightly earlier, 
but since it too is related, like all the rest of these features, to the sub- 
marine continental border it would seem that it must ultimately be re- 
ferred to the same time. 
We have now run briefly over four distinct groups of facts derived 
directly from geological observation by various observers who speak 
independently and collectively of elevation followed by subsidence of 
various lands relative to the level of the sea. The figures, as far as we 
have any, are in thousands of feet, averaging roughly a mile or more. 
The timing, as far as we have it, is in close agreement over wide ranges 
of latitude and longitude. But suppose we question that last point. 
Are we not familiar with slow elevation or depression of various coasts? 
The sea is said to be losing today along some of the coasts of South 
America and Scandinavia and gaining on Iceland and Greenland. 
It has not yet been definitely proved that the glaciation which in- 
volved the southern lands was simultaneous with that of the North. 
Dr. Croll and even Darwin thought that the facts would be as well 
explained by alternate glaciations of the northern and southern hemi- 
spheres. Of course the opinions of Hartt and Agassiz may constitute 
more than an offset for this but it should be borne in mind nevertheless. 
The elevation of North America and northwestern Europe have, I 
believe without dispute, been made coeval and conterminate with the 
glaciation of those regions and with each other. Further on we shall 
see that the concensus of opinion is strongly toward the conclusion that 
Dana arrived at and that was expressed by Hartt and Agassiz that these 
movements, even though widely distributed, are all essentially related 
and essentially simultaneous. 
Let us turn now for a moment from the contemplation of the rocks, 
the glaciers and the rivers to compare with what we have found the dis- 
tribution of those plants and animals whose evolution and spread, 
whose very existence is inseparably linked with these geological and 
geographical features. If we are conscious of any feeling of distrust, 
distributional data seeming less capable of carrying us safely through 
critical investigations, it may in part be dispelled by recalling how 
completely in its progress inorganic geology has been intertwined with 
palaeontology and how thoroughly the living world has been investigated 
by an army of careful students. I venture to think that, with care, dis- 
tributional data may be made to yield results hardly less valuable than 
those of a purely geological nature. 
(b) biological evidence of former elevation. 
The second division of the evidence which, as we shall see, accords 
with the first in indicating a former higher altitude above the sea of 
