For there could not have been
surface-drainage to make them all, or a tenth of them. There are no
other possible hypotheses; and so he must fall back on the original
theory--the rain, the springs, the brook; they have done it all, even as
they are doing it this day.

But is not that still a hasty assumption? May not their denuding power
have been far greater in old times than now?

Why should it? Because there was more rain then than now? That he must
put out of court; there is no evidence of it whatsoever.

Because the land was more friable originally? Well, there is a great
deal to be said for that. The experience of every countryman tells him
that bare or fallow land is more easily washed away than land under
vegetation. And no doubt, when these gravels and sands rose from the
sea, they were barren for hundreds of years. He has some measure of the
time required, because he can tell roughly how long it takes for sands
and shingles left by the sea to become covered with vegetation. But he
must allow that the friability of the land must have been originally much
greater than now, for hundreds of years.

But again, does that fact really cut off any great space of time from his
hundreds of thousands of years? For when the land first rose from the
sea, that glen was not there. Some slight bay or bend in the shore
determined its site. That stream was not there. It was split up into a
million little springs, oozing side by side from the shore, and having
each a very minute denuding power, which kept continually increasing by
combination as the glen ate its way inwards, and the rainfall drained by
all these little springs was collected into the one central stream. So
that when the ground being bare was most liable to be denuded, the water
was least able to do it; and as the denuding power of the water
increased, the land, being covered with vegetation, became more and more
able to resist it. All this he has seen, going on at the present day, in
the similar gullies worn in the soft strata of the South Hampshire coast;
especially round Bournemouth.

So the two disturbing elements in the calculation may be fairly set off
against each other, as making a difference of only a few thousands or
tens of thousands of years either way; and the age of the glen may fairly
be, if not a million years, yet such a length of years as mankind still
speak of with bated breath, as if forsooth it would do them some harm.

I tr