Where did it come from?

That is what I propose to discuss with you in this work,--if you will
have the patience to follow me.

So far as possible, [as I shall in all cases speak by the voices of
others] I shall summon my witnesses that you may cross-examine them.
I shall try, to the best of my ability, to buttress every opinion
with adequate proofs. If I do not convince, I hope at least to
interest you.

And to begin: let us understand what the Drift _is_, before we
proceed to discuss its origin.

In the first place, it is mainly unstratified; its lower formation is
altogether so. There may be clearly defined strata here and there in
it, but they are such as a tempest might make, working in a
dust-heap: picking up a patch here and laying it upon another there.
But there

{p. 3}

are no continuous layers reaching over any large extent of country.

Sometimes the material has been subsequently worked over by rivers,
and been distributed over limited areas in strata, as in and around
the beds of streams.

But in the lower, older, and first-laid-down portion of the Drift,
called in Scotland "the till," and in other countries "the hard-pan,"