COMMUNICATION DE M. WARREN IJPIIAM 
239 
The first and second of these periods, which were comparative- 
V long-, constituted tlie Pleistoccne division, while the tliird 
and very brief period is the Présent or Psycliozoic division, of 
fhe Quaternary era. 
EpEIROGENIG MoVEMENTS ASSOCIATED WITII GLACIATION. 
The theory of the causes of the Ice âge which lias been suc- 
Çessively advocated, in terms varying with increasing laiowledge, 
Eyell, Dana, Le Conte, Wright, .laniieson, and othcrs, in- 
^luding the présent writer, is called tlie Earlli Movenient hypo- 
^hesis^ by Prof. James Geikie, who lias adversely criticized it. 
ccording to this explanation, the accumulation of the ice-sheets 
yas due to uplifts of the land as extensive high plateaus receiv- 
^*^8' snowfall throiighoiit the year. Geology is indebted to Gilbert 
his U. S. Geological Survey inonograph : Lake Bonneville, 
the terms epeirogeny and epeirogenic (continent-produciug), 
0 designate the broad movemeiits of uplift and subsidence 
affect the whole or large portions of continental areas or 
° fhe oceanic basins. Tins view, accoiinting for glaciation by 
^*8h altitude, may therefore be very properly named the epei- 
*^®8®nic theory. 
|n the first édition of the Principles of Geology (1830), Lyell 
Pointed ont the intimate dependcnce of climate upon tlie distri- 
atioii of areas of land and water and upon tlie altitude of tlie 
in 1^05, Dana, reasoning from the prevaicnce of fjords 
nll glaciated régions and showing that thèse are valleys crod- 
V streams during a formerly greater élévation of the land 
P^evious to glaciation, and from the marine beds of the St. Law- 
î'^nce valley and basin of lake Ghamplain belonging to the Unie 
following the glaciation, announced that the forma- 
of the drift in North America was attended by three great 
ice ^**^®*^*'®* movements : the first upward, during which the 
^“sheet was accumulated on the land ; the second downward, 
the ice-sheet was melted awav ; and the tliird, withiii r 
g time, a re-elevation, bringing the land to its présent height 
jjff nioderate depth of the fjords and submarine val- 
l^ys then known, the amountof preglacial élévation which could 
fhus affirmed was evidently too little to be an adéquate cause 
Joy Assoc. for Adv. of Science, vol. IX, for 1855, p- 28, 29 ; Am. 
■■“al of Science, II, vol. XXII, p. 3-28, 329, Nov. 1850. 
re- 
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