230 The American (leohxjist. October, 1893 
these stages of halt or re-advance being marked by the 
moraines. 
Mr. W J McGee congratulated the Congress on having so 
Large a series of papers from observers and explorers of the 
glacial drift, giving the results of their inductive studies. 
Major C. E. Dtjtton cautioned glacialists against proceed- 
ing further with theories than the observed facts warrant. 
He believes that it is yet too early to assign safely the causes 
of the Ice age; but he cannot accept the astronomic theory 
of Croll and Geikie, and inclines to look rather to geographic 
conditions. The careful notation of observations should be 
continued, with less of hasty interpretations and generaliza- 
tion. 
Prof. Chamberlin, summing up the main conclusions of 
these papers, stated that his view of the Ice age in the 
United States gives it a tripartite division, two epochs of gla- 
ciation having preceded the longest of the interglacial 
epochs. He agrees somewhat nearly with Hansen and Heim, 
making the early times of glaciation long and the ice in the 
middle glacial epoch more extensive than in the latest, to 
which the moraines mostly belong. 
Prof. Salisbury remarked that a distinct glacial epoch need 
not comprise a long time in a geologic sense, but may be dis- 
tinguished by important though not prolonged changes in the 
conditions of the ice action, attitude of the land, and processes 
of drift accumulation. Forest beds enclosed in till might be 
formed in Alaska, near the seaboard, by short ice advances; 
but the forest beds of Iowa and Illinois, in the interior of the 
continent, imply truly interglacial followed by glacial 
climates. The comparative depths of oxidation of the earty 
and late drift indicate a very long interval between their 
epochs of formation. 
Mr. Leverett replied to Prof. Wright's suggestion concern- 
ing the parallelism of the successive boundaries of the ice, 
that in Illinois notable irregularities and intercrossing occur 
in the courses of the four outer border lines which he has 
traced. 
The papers and their discussion extended this session to 
1:30 p. m., when the Congress adjourned, without taking up 
the question proposed at the end of the program for a special 
