This, then, is, briefly stated, the condition of the Drift.

It is plain that it was the result of violent action of some kind.

And this action must have taken place upon an unparalleled and
continental scale. One writer describes it as,

"A remarkable and stupendous period--a period so startling that it
might justly be accepted with hesitation, were not the conception
unavoidable before a series of facts as extraordinary as itself."[2]

Remember, then, in the discussions which follow, that if the theories
advanced are gigantic, the facts they seek to explain are not less
so. We are not dealing with little things. The phenomena are
continental, world-wide, globe-embracing.

[1. Dana's "Text-Book," p. 221.

2. Gratacap, "Ice Age," "Popular Science Monthly," January, 1878.]

CHAPTER II.

THE ORIGIN OF THE DRIFT NOT KNOWN.

WHILE several different origins have been assigned for the phenomena
known as "the Drift," and while one or two of these have been widely
accepted and taught in our schools as established truths, yet it is
not too much to say that no one of them meets all the requirements of
the case, or is assented to by the profoundest thinkers of our day.