instinct which makes a little dog run away from a big dog. Be that
as it may, every observer has it; and so the man's conclusion seems
to him strange, doubtful: he will reconsider it.

Moreover, if he be an experienced man, he is well aware that first
guesses, first hypotheses, are not always the right ones; and if he
be a modest man, he will consider the fact that many thousands of
thoughtful men in all ages, and many thousands still, would say,
that the glen can only be a few thousand, or possibly a few hundred,
years old. And he will feel bound to consider their opinion; as far
as it is, like his own, drawn from facts, but no further.

So he casts about for all other methods by which the glen may have
been produced, to see if any one of them will account for it in a
shorter time.

1. Was it made by an earthquake? No; for the strata on both sides
are identical, at the same level, and in the same plane.

2. Or by a mighty current? If so, the flood must have run in at
the upper end, before it ran out at the lower. But nothing has run
in at the upper end. All round above are the undisturbed gravel-
beds of the horizontal moor, without channel or depression.

3. Or by water draining off a vast flat as it was upheaved out of
the sea? That is a likely guess. The valley at its upper end
spreads out like the fingers of a hand, as the gullies in tide-muds
do.

But that hypothesis will not stand. There is no vast unbroken flat