comet which struck the earth was much larger than Donati's comet, and
we have the means of accounting for results as prodigious as those
referred to.

We have seen that it is difficult to suppose that ice produced the
drift-deposits, because they are not found where ice certainly was,
and they are found where ice certainly was not. But, if the reader
will turn to the

[1. "Elements of Geology," pp. 168,171, _et seq_.

2. "The Heavens," p. 260.]

{p. 97}

illustration which constitutes the frontispiece of this volume, and
the foregoing engraving on page 93, he will see that the Drift is
deposited on the earth, as it might have been if it had suddenly
fallen from the heavens; that is, it is on one side of the globe--to
wit, the side that faced the comet as it came on. I think this map is
substantially accurate. There is, however, an absence of authorities
as to the details of the drift-distribution. But, if my theory is
correct, the Drift probably fell at once. If it had been twenty-four
hours in falling, the diurnal revolution would, in turn, have
presented all sides of the earth to it, and the Drift would be found
everywhere. And this is in accordance with what we know of the rapid
movements of comets. They travel, as I have shown, at the rate of
three hundred and sixty-six miles per second; this is equal to
twenty-one thousand six hundred miles per minute, and one million two
hundred and ninety-six thousand miles per hour!