a few older geologists, speak lightly of the
"nightmare" of the Ice-Age. But the age has gone by in which it could
seriously be suggested that the boulders strewn along the east of
Scotland--fragments of rock whose home we must seek in Scandinavia--were
brought by the vikings as ballast for their ships. Even the more serious
controversy, whether the scratches and the boulders which we find on the
face of Northern Europe and America were due to floating or land ice,
is virtually settled. Several decades of research have detected the
unmistakable signs of glacial action over this vast area of the northern
hemisphere. Most of Europe north of the Thames and the Danube, nearly
all Canada and a very large part of the United States, and a somewhat
less expanse of Northern Asia, bear to this day the deep scars of
the thick, moving ice-sheets. Exposed rock-surfaces are ground and
scratched, beds of pebbles are twisted and contorted hollows are scooped
out, and moraines--the rubbish-heaps of the glaciers--are found on every
side. There is now not the least doubt that, where the great Deinosaurs
had floundered in semi-tropical swamps, where the figs and magnolias had
later flourished, where the most industrious and prosperous hives of
men are found to-day, there was, in the Pleistocene period, a country to
which no parallel can be found outside the polar circles to-day.

The great revolution begins with the gathering of snows on the
mountains. The Alps and Pyrenees had now, we saw, reached their full
stature, and the gathering snows on their summits began to glide
down toward the plains in rivers of ice. The Apennines (and even the
mountains of Corsica), the Balkans, Carpathians, Caucasus, and Ural
Mountains, shone in similar mantles of ice and snow. The mountains of
Wales, the north of England, Scotland, and Scandinavia had even heavier
burdens, and, as the period advanced, their sluggish streams of
ice poured slowly over the plains. The trees struggled against the
increasing cold in the narrowing tracts of green; the animals died,
migrated to the south, or put on arctic coats. At length the ice-sheets
of Scandinavia met the spreading sheets from Scotland and Wales, and
crept over Russia and Germany, and an almost continuous mantle, from
which only a few large areas of arctic vegetation peeped out, was thrown
over the greater part of Europe. Ten thousand feet thick where it left
the hills of Norway and Sweden, several thousand fe