Man in the Ice Age. — Upham. 147 
may be confidently accepted as the approximate duration of 
Postglacial time. For the antiquity of man at Trenton and at 
Little Falls, it may be stated as about 7,000 years. If we should 
adopt the ratio given by Chamberlin, who estimates the lowan 
stage as five times as long ago,* it would give the antiquity of 
the Lansing fossil man as about 35,000 years, agreeing with 
the first newspaper estimate before mentioned. 
My studies of the glacial Lake Agassiz, however, warrant 
no longer time for its duration than 1,000 years, f On a similar 
scale. I think the time of glacial recession from the lowan stage 
to the north end of Lake Agassiz may be no more than 5.000 
years, giving a date about 12,000 years ago for the Lansing 
man and the loess. Further back, I may also give my estimates 
of the earlier parts of the Glacial period, as about 10,000 years 
for the growth of the icefields during the lowan stage, before 
the Champlain subsidence caused them to melt and supply the 
loess in its chief abundance ; about 10,000 years for the pre- 
ceding Helvetian or Buchanan glacial retreat, giving thus some 
25,000 years before the end of the Ice age as the time of the 
Kansan maximum glaciation ; a previous slow ice accumulation 
and transportation of the Kansan glacial drifi, that is, the Kan- 
san stage of the Ice age,also about 25,000 years ; the previous 
Aftonian stage of glacial recession, another such allowance of 
about 25,000 years; and, earliest of all, the Albertan stage of 
ice accumulation and formation of its drift deposits, likewise 
about 25,000 years. All the Ice age I would thus comprise 
within about 100,000 years. This estimate seems to harmonize 
well with the geologic time ratios of Dana, Walcott, and others, 
which indicate about a hundred million years as the duration of 
life on our globe. 
Man in the Somme valley and other parts of France, and in 
southern England, made good pakeolithic implements fully 
100,000 years ago, according to my estimate of the length of 
the Ice age. J When the earliest men came to America cannot 
probably be closely determined. It was during the Glacial per- 
iod, or possibly earlier. The Lansing skeleton affords probably 
our oldest proof of man's presence on this continent ; but it is 
*Journal of Geology, vol. iv, pp. 872-876, Oct. -Nov.. 1S96. 
■f-r/. S. Geol. Survey, Monograph xxv, 1895, pp. 200, 210, 225, 238-24-4-. 
tAm. Geologist, vol. xxii, pp. 350-362, Dec, 1898. 
