dation,
that Central Europe, England, Scotland, and Ireland had been buried
beneath solid ice; that from the mountain-tops of Scandinavia, the
Grampians of Scotland, the Lake Hills of England, and the summits of
the Alps had proceeded rivers of ice, whose confluent seas swept over
Europe and grooved it with valleys, channeled the courses of its
rivers, engraved its rocks, scooped out its lakes, and scattered their
burden of débris far and wide over its plains. The conception was a
bold, almost a terrifying one, and because the actual history and
nature of glaciers were so little known it was regarded with aversion
and spoken of with contempt. Agassiz had laboriously studied the
glaciers of the Alps, and he knew so well their character and their
physiographic significance that he recognized elsewhere the evidence of
their past presence.
Venetz,
Rendu, and Charpentier had preceded him in glacial study and had
insisted upon an extension of the Alpine glaciers far beyond their
present beds in past ages, but had not realized the immense utility of
these views in explaining the glaciated surfaces of Europe. Forbes,
Hopkins, and Tyndall succeeded him in the investigation of glacial
physics, and by their close scrutiny into the constitution of ice and
the laws of ice making and glacial motion fairly established a new
department of physical science and added confirmation to the views of
Agassiz.
Let
us examine some of these singular and hitherto inexplicable records
which elicited Agassiz's theory and which, long before they were
harmonized by that assumption, had been attentively examined by
geologists and explained upon other grounds.
The
rocks as they lie in place, the flanks and summits of mountains to
heights of 5,000 and 10,000 feet, and the surfaces of outcropping
masses over immense areas of the world, are gouged with channels
sometimes a foot deep, sometimes eight feet deep, with widths from two
to three feet. These grooves, of all dimensions, pass over the rocks in
groups, like
