AM ts Mo NATU RALISI 
VoL. E cu December, 1894. 336 
QUATERNARY TIME DIVISIBLE IN THREE PERIODS, 
THE LAFAYETTE, GLACIAL, AND RECENT: 
By WARREN UPHAM. 
According to definitions in text-books by Dana, Archibald 
Geikie and Etheridge, the Quaternary era began with the 
change from the mild Pliocene climate to that of the Glacial 
period, with its accumulation of the vast sheets of land ice in 
high latitudes, and has continued to the present time. We 
are living in the Quaternary era, as thus defined, and it must 
extend far into the future to be at all proportionate in length 
with the previous co-ordinate divisions of geologic time. 
Le Conte and Prestwich, however, consider the Quaternary 
division of time as completed at the dawn of civilization, with 
traditional and written history; and they assign recent geolo- 
gic changes to a new era, named by Le Conte the Psychozoic, 
which is separated from the preceding principally on account 
of the supremacy of man. The former’ view seems preferable, 
because man is known to have been contemporaneous with the 
Ice age. 
Quaternary time, therefore, is here assumed to include (1) 
the period of changed conditions causing the accumulation of 
‘Presented before Section E of the American Association for the Advancement 
of Science at the Brooklyn meeting, August 20, 1894; also partly contained in a 
paper read before the Geological Society of America, August 16, 1893, as pub- 
lished in = Bulletin, Vol. V, pp. 87-100, January, 1894. 
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