harbors enlivened by the
commerce of the world, or ripening fields attesting the vivifying
influence of a genial sun. Let us, therefore, follow after the leaders
in thought. When we come to where they can not agree we can at least see
what both sides have to say.

Somewhat at the risk of repetition, we will try and impress on our
readers a sense of the reality and severity of the Glacial Age. There is
danger in regarding this as simply a convenient theory that geologists
have originated to explain some puzzling facts, that it is not very
well founded, and is liable to give way any day to some more ingenious
explanation. On the contrary, this whole matter has been worked out by
very careful scholars. There is, perhaps, no great conclusion in any
science which rests upon a surer foundation than this, and if we are to
be guided by our reason at all in deducting the unknown from the known,
the past from the present, we can not refuse our assent to the reality
of the Glacial Age of the Northern Hemisphere in all its more important
features.<2> At the present day glaciers do exist in several places on
the earth. They are found in the Alps and the mountains of Norway, and
the Caucasus, in Europe. The Himalaya mountains support immense glaciers
in Asia; and in America a few still linger in the more inaccessible
heights of the Sierra Nevada. It is from a study of these glaciers,
mainly however, those of the Alps, that geologists have been enabled to
explain the true meaning of certain formations they find in both Europe
and America, that go by the name of drift.

When in an Alpine valley we come upon a glacier, filling it from side to
side, there will be noticed upon both sides a long train of rock, drift,
and other _debris_ that have fallen down upon its surface from the
mountain sides. If two of these ice-rivers unite to form one glacier,
two of these trains will then be borne along in the middle of the
resulting glacier. As this glacier continues down the valley, it at
length reaches a point where a further advance is rendered impossible
by the increased temperature melting the ice as fast as it advances. At
this point the train of rocks and dirt are dumped, and of course form
great mounds, called moraines. The glacier at times shrinks back on its
rocky bed and allows explorers to examine it.

In such cases they find the rocks smoothed and polished, but here and
there marked with long grooves and striae. These points are l