304 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1914. 
at the close of the Eocene in the Pyrenees, and in the Miocene the 
entire ‘‘Alpine system” was in elevation. This unrest spread at 
the same time to the Caucasus, Asia, and to the entire Himalayan 
region of highest mountams and elevated plateaus, an area 22° 
of latitude in width. Itis probable that all of the world’s great moun- 
tain chains were more or less reelevated in Miocene and Pliocene 
times, resulting in the present abnormally high stand of the continents 
when contrasted with the oceanic mean level. 
These elevations also-altered the continental connections, for 
North and South America were reunited in Miocene times, and west- 
ern Europe, Greenland, and America were severed late in the Tertiary 
era, the exact time being as yet not clearly established. With these 
ereat changes also must have come about marked alterations in the 
oceanic currents and, as a consequence, in the distribution of heat 
and moisture over vast areas of the northern Atlantic lands. It is 
admitted by all paleontologists that the marine waters of late Pliocene 
times in the arctic region were cool, and the widespread glacial tills 
of the Northern Hemisphere are evidence of a glacial climate of 
varying intensity throughout Pleistocene time. 
CONCLUSIONS. 
Our studies of the paleometeorology of the earth are summed up 
in figure 4. We have seen that two marked glacial periods are 
clearly established. The one best known was of Pleistocene time 
and the other, less well known in detail, of earliest Permic time. 
Both were world-wide in their effects, reducing the mean temperatures 
sufficiently to allow vast accumulations of snow and ice, not only 
at high altitudes, but even more markedly at low levels, with the 
glaciers in many places attaining the sea. We also learn that the 
continental glaciers of Pleistocene time were dominant in polar regions 
while those of Permic time had their greatest spread from 20° to 40° 
south of the present equator, and to a far less extent between 20° and 
40° in the other hemisphere. There is also some evidence of glaciers 
in equatorial Africa in Permic time. We may further state that, 
although Pleistocene glaciation was general in the arctic region, 
there certainly was none at this pole in early Permic time, because 
of the widespread and abundant marine faunas that are not markedly 
unlike those of the Upper Carbonic; asfor the South Pole, our knowl- 
edge of pre-Pleistocene glaciation is as yet a blank. 
A glacial period does not appear to remain constantly cold, but 
fluctuates between cold glacial climates and warmer interglacial 
times of varying duration. During the Pleistocene there were, 
according to the best glaciologists, at least three, if not four, such 
warmer intervals. The Permic glacial period also had its warmer 
