10 BUREAU OF AMERICAN ETHNOLOGY [BULL. 33 
istic in the regions over which the glaciers extended. These forma- 
tions include especially the so-called glacial gravels which have 
received particular attention at the hands of students of early @ 
man in this country. 
The several irregular ice invasions extended at their maximum as 
far south on the Atlantic coast as Long Island. In the Delaware 
valley they reached Easton, Pennsylvania; in the Ohio valley, Cin- 
cinnati, Ohio; and in the Missouri valley, the vicinity of St. Louis. 
Beginning with the earliest subdivision, the several successive stages 
of this period, with the few and uncertain chronological approxima- 
tions that have been made, are thus given by leading American 
geologists: ? 
Time in years since cli- 
i b y , max was reached 
I. The Sub-Aftonian, or Jerseyan, the earliest known 
LD VASLOM 25 oe 1S ie tak eye ee ce 2a) 
II. The Aftonian, the first known interglacial interval_ (?) 
Ill. The Kansan, or second invasion now recognized___ 300, 000 to 1, 020, 000 
IV. The Yarmouth, or Buchanan, the second interglacial 
imbeteyalll st ae c eee A ee ele Woe ee ne Gee (?) 
V.ethe ilinoian, the:third invasion. s+ se besos! ou 140, 000 to 540, 000 
VI. The Sangamon, the third interglacial interval______ (?) 
Vil’ The Towan, the fourth invasion 0-2-2 60, 000 to 300, 000 
VIII. The Peorian, the fourth interglacial interval_______ (7?) 
IX. The Earlier Wisconsin, the fifth invasion___.______ 40, 000 to 150, 000 
X. The fifth interval of deglaciation, as yet unnamed__ (?) 
XI. The Later Wisconsin, the sixth advance___________ 20, 000 to 60, 000 
XII. The Glacio-Lacustrine substage. 
XII. The Champlain substage. 
The glacial invasion closed apparently with a gradual recession of 
the ice, and thus terminated considerably earlier in southern than in 
northern latitudes; this should be kept in mind in considering the 
date of the ultimate disappearance of the ice in any limited region. 
The precise date of the final recession of ice in any locality must 
always remain in a large degree conjectural. The climax of the 
final, or Champlain substage, in the latitude of the St. Lawrence 
river, was apparently reached considerably more than ten thousand 
years ago.° : 
Should it be assumed that man existed on the North American 
continent before the present geological period, and taking into account 
his osseous remains only, two important questions arise, namely, where 
“The term early, as employed in this paper, applies only to the Pleistocene and older 
geological periods. 
» After Thomas C. Chamberlin and R. D. Salisbury’s Geology, 111, 383, 420, New York, 
1906 ; reversed in arrangement. See also Salisbury’s The Glacial Geology of New Jersey, 
Geological Survey of New Jersey, v, Trenton, 1902. It should not be understood that all 
of the given divisions apply to the entire vast glaciated area; some of the terms relate 
only to somewhat localized phases of the period. 
°A summary of the whole question of estimates by years is given in the chapter on 
the Glacial period in volume rr of Chamberlin and Salisbury’s Geology. 
