ce in an undisturbed deposit, and could not have found their
way thither in any recent time; Dr. Abbott assigned them to the age of
the Glacial drift. This was the beginning of a long series of
investigations, in which Dr. Abbott's work was assisted and supplemented
by Messrs. Whitney, Carr, Putnam, Shaler, Lewis, Wright, Haynes,
Dawkins, and other eminent geologists and archaeologists. By 1888 Dr.
Abbott had obtained not less than 60 implements from various recorded
depths in the gravel, while many others were found at depths not
recorded or in the talus of the banks.[8] Three human skulls and other
bones, along with the tusk of a mastodon, have been discovered in the
same gravel. Careful studies have been made of the conditions under
which the gravel-banks were deposited and their probable age; and it is
generally agreed that they date from the later portion of the Glacial
period, or about the time of the final recession of the ice-sheet from
this region. At that time, in its climate and general aspect, New York
harbour must have been much like a Greenland fiord of the present day.
In 1883 Professor Wright of Oberlin, after a careful study of the
Trenton deposits and their relations to the terrace and gravel deposits
to the westward, predicted that similar palaeolithic implements would be
found in Ohio. Two years afterward, the prediction was verified by Dr.
Metz, who found a true palaeolith of black flint at Madisonville, in the
Little Miami valley, eight feet below the surface. Since then further
discoveries have been made in the same neighbourhood by Dr. Metz, and in
Jackson county, Indiana, by Mr. H. T. Cresson; and the existence of man
in that part of America toward the close of the Glacial period may be
regarded as definitely established. The discoveries of Miss Babbitt and
Professor Winchell, in Minnesota, carry the conclusion still farther,
and add to the probability of the existence of a human population all
the way from the Atlantic coast to the upper Mississippi valley at that
remote antiquity.

[Footnote 8: Wright's _Ice Age in North America_, p. 516.]

[Sidenote: and in Delaware.]

A still more remarkable discovery was made by Mr. Cresson in July, 1887,
at Claymont, in the north of Delaware. In a deep cut of the Baltimore
and Ohio Railroad, in a stratum of Philadelphia red gravel and brick
clay, Mr. Cresson obtained an unquestionable palaeolith, and a few months
afterward his diligent search wa