Man and the Glacial PeriodWright, G. Frederick (George Frederick)
History
Man and the Glacial Period
Wright, G. Frederick (George Frederick)
Glacial epoch; Prehistoric peoples
[Footnote DV: Nature (August 26, 1880), vol. xxii, pp. 388, 389.]
Still, this evidence is less abundant than we should expect, if there had
been the repeated Glacial epochs supposed by Mr. Croll's astronomical
theory; and it is by no means impossible that the conglomerates of
scratched stones described by Professor Ramsey in Great Britain, and
by Messrs. Blandford and Medlicott in India, may have resulted from
local glaciers coming down from mountain-chains which have been since
removed by erosion or subsidence. We are not aware that any incontestable
evidence has been presented in America of any glaciation previous to that
of _the_ Glacial period.
Upon close consideration, also, it appears that Mr. Croll's theory has
not properly taken into account the anomalous distribution of heat which
we actually find to take place on the surface of the earth. He has done
good service in showing what an enormous transfer of heat there is
from the southern to the northern Atlantic by means of the Gulf Stream,
estimating that the heat conveyed by the Gulf Stream into the Atlantic
Ocean is equal to one fifth of all possessed by the waters of the North
Atlantic; or to the heat received from the sun upon a million and a half
square miles at the equator, or two million square miles in the temperate
zone. "The stoppage of the Gulf Stream would deprive the Atlantic of
77,479,650,000,000,000,000 foot-pounds of energy in the form of heat per
day."
Among the objections which bear against this ingenious theory is one
which will appear with great force when we come to discuss the date of
the Glacial period, when we shall show that even Professor Hitchcock's
supposition that the lingering effects of the last great eccentricity of
the earth's orbit, continued down to forty thousand years ago, is not
sufficient to account for the recentness of the close of the period as
shown by abundant geological evidence. It is certainly not more than ten
or fifteen thousand years ago that the ice finally melted off from the
Laurentian highlands; while on the Pacific coast the period of glaciation
was still more recent.
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