as it reached during the Glacial epoch. For the
last 50,000 years the departure of the earth's orbit from a circular
form has been exceptionally small.

[Footnote 4: _Excursions of an Evolutionist_, p. 39.]

[Footnote 5: Croll, _Climate and Time in their Geological
Relations_, New York, 1875; _Discussions on Climate and
Cosmology_, New York, 1886; Archibald Geikie, _Text Book of
Geology_, pp. 23-29, 883-909, London, 1882; James Geikie, _The
Great Ice Age_, pp. 94-136, New York, 1874; _Prehistoric
Europe_, pp. 558-562, London, 1881; Wallace, _Island Life_, pp.
101-225, New York, 1881. Some objections to Croll's theory may
be found in Wright's _Ice Age in North America_, pp. 405-505,
585-595, New York, 1889. I have given a brief account of the
theory in my _Excursions of an Evolutionist_, pp. 57-76.]

Now the traces of the existence of men in North America during the
Glacial epoch have in recent years been discovered in abundance, as for
example, the palaeolithic quartzite implements found in the drift near
the city of St. Paul, which date from toward the close of the Glacial
epoch[6]; the fragment of a human jaw found in the red clay deposited in
Minnesota during an earlier part of that epoch;[7] the noble collection
of palaeoliths found by Dr. C. C. Abbott in the Trenton gravels in New
Jersey; and the more recent discoveries of Dr. Metz and Mr. H. T.
Cresson.

[Footnote 6: See Miss F. E. Babbitt, "Vestiges of Glacial Man
in Minnesota," in _Proceedings of the American Association_,
vol. xxxii., 1883.]

[Footnote 7: See N. H. Winchell, _Annual Report of the State
Geologist of Minnesota_, 1877, p. 60.]

[Sidenote: Discoveries in the Trenton gravel.]

[Sidenote: Discoveries in Ohio, Indiana, and Minnesota;]

The year 1873 marks an era in American archaeology as memorable as the
year 1841 in the investigation of the antiquity of man in Europe. With
reference to these problems Dr. Abbott occupies a position similar to
that of Boucher de Perthes in the Old World, and the Trenton valley is
coming to be classic ground, like the valley of the Somme. In April,
1873, Dr. Abbott published his description of three rude implements
which he had found some sixteen feet below the surface of the ground "in
the gravels of a bluff overlooking the Delaware river." The implements
were in pla