as
come to believe, far beyond the Alps. If the Alps had been covered with
an ice sheet, so had many other regions of the northern hemisphere.
Casting abroad for evidences of glacial action, Agassiz found them
everywhere in the form of transported erratics, scratched and polished
outcropping rocks, and moraine-like deposits. Finally, he became
convinced that the ice sheet that covered the Alps had spread over the
whole of the higher latitudes of the northern hemisphere, forming an
ice cap over the globe. Thus the common-sense induction of the
chamois-hunter blossomed in the mind of Agassiz into the conception of a
universal ice age.

In 1837 Agassiz had introduced his theory to the world, in a paper read
at Neuchatel, and three years later he published his famous Etudes sur
les Glaciers, from which we have just quoted. Never did idea make a more
profound disturbance in the scientific world. Von Buch treated it
with alternate ridicule, contempt, and rage; Murchison opposed it with
customary vigor; even Lyell, whose most remarkable mental endowment was
an unfailing receptiveness to new truths, could not at once discard
his iceberg theory in favor of the new claimant. Dr. Buckland, however,
after Agassiz had shown him evidence of former glacial action in his own
Scotland, became a convert--the more readily, perhaps, as it seemed to
him to oppose the uniformitarian idea. Gradually others fell in line,
and after the usual imbittered controversy and the inevitable full
generation of probation, the idea of an ice age took its place among
the accepted tenets of geology. All manner of moot points still demanded
attention--the cause of the ice age, the exact extent of the ice sheet,
the precise manner in which it produced its effects, and the exact
nature of these effects; and not all of these have even yet been
determined. But, details aside, the ice age now has full recognition
from geologists as an historical period. There may have been many ice
ages, as Dr. Croll contends; there was surely one; and the conception
of such a period is one of the very few ideas of our century that no
previous century had even so much as faintly adumbrated.

THE GEOLOGICAL AGES

But, for that matter, the entire subject of historical geology is
one that had but the barest beginning before our century. Until the
paleontologist found out the key to the earth's chronology, no one--not
even Hutton--could have any definite idea as to the true stor