882 The American Naturalist. [October, 
of America. It isa difficult subject of unusual interest, and it promises 
to be epoch making in the department of dynamical and recent geology. 
Two previous papers by myself have been published by the Society upon 
topics leading up to the present investigations, which take into considera- 
tion the characteristices of the valleys both of the southern mountains 
and the coastal plains,and show how the valley directly due to atmos- 
pheric erosion. All of the land valleys become miles in width in their 
lower reaches, where they are buried by recent accumulations of sand, 
ete., to considerable depths. Off the coast there are broad submerged 
plateaus or terraces marking the pauses in the changes of sea level. 
Across these plateaus are numerous drowned canons or fjords shown 
to reach to very great depths. From their resemblance to the land val- 
leys, they are regarded as of atmospheric or erosion origin, After 
passing the limits of the sands shifted by the coastal currents and fill- 
ing the valleys, it may be said that every great valley has its fjord-like 
continuation through the submerged margin of the continental mass, 
even to depths of 10,000 or 12,000 ft. or more. From the natural infer- 
ence that these valleys were formed above sea level, it would appear 
that the land had stood as high as the fjords are deep. But this state- 
ment is modified, for the movements have been in unequal undulations, 
the amount of which can often be calculated, and thereby the extreme 
depth has been reduced so that it seems that the former elevations of 
the West Indian region and adjacent parts of the continent may not 
have stood more than from 8,000 to 12,000 feet higher than now, 
according to the locality. The undulations of the earth’s crust have 
been exaggerated by mountain folds in places, but in the great majority 
of the drowned valleys, such has not obtained for their direction is not 
parallel to the mountain ridges, but across that of the continental mass. 
Consequently there is no escape from the conclusion that the late con- 
tinental elevation is measureable, but the movement has proved to be 
vastly greater than had hitherto been supposed, enough to change the 
whole physical geography of the region, the climate and the conditions 
of life. During the epochs of elevation, the Mexican Gulf and the 
Caribbean Sea were dry plains which extended to and were drained 
into the Pacific Ocean. The Antillean Islands formed a plateau-bridge 
connecting the two Americas. 
At the close of the Miocene period, the Antillean and Central 
American lands were represented by only small islands. Then suc- 
ceeded the Pliocene period during the earlier and mid portion of which 
the great elevation occurred. This was succeeded by the subsidence 
about the close of the Pliocene period, long enough to allow the 
