cases no rocks of the same material are found within two hundred miles.
These two formations—the “till” and the “bowlder-clay”—sometimes pass into each other by insensible degrees. At other times the distinction is marked. Some of the stones in the bowlder-clay are furrowed or striated, but a large part of them are not; while in the “till” the stone not striated is the rare exception.
Above this bowlder-clay we find sometimes beds of loose gravel, sand, and stones, mixed with the remains of man and other animals. These have all the appearance of being later in their deposition, and of having been worked over by the action of water and ice.
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."
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.]
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.
Says one authority:
“The origin of the unstratified drift is a question which has been much controverted."
Louis Figuier says, after considering one of the proposed theories:
“No such hypothesis is sufficient to explain either the cataclysms or the glacial phenomena; and we need not hesitate to confess our ignorance of this strange, this mysterious episode in the history of our globe. . . . Nevertheless, we repeat, no explanation presents itself which can be considered conclusive; and in science we should never be afraid to say, I do not know.”
“Many geologists can not yet be persuaded that till has ever formed and accumulated under ice.” 
A recent scientific writer, after summing up all the facts and all the arguments, makes this confession:
[1. “American Cyclopædia,” vol. vi, p. 112.
2. “The World before the Deluge,” pp. 435, 463.