ght through the chalk, and drain the water out of the flat vale
behind us. But I suspect the sea helped him somewhat, or perhaps a great
deal, just where we are now.

The sea?

Yes. The sea was once--and that not so very long ago--right up here,
beyond Reading. This is the uppermost end of the great Thames valley,
which must have been an estuary--a tide flat, like the mouth of the
Severn, with the sea eating along at the foot of all the hills. And if
the land sunk only some fifty feet,--which is a very little indeed,
child, in this huge, ever-changing world,--then the tide would come up to
Reading again, and the greater part of London and the county of Middlesex
be drowned in salt water.

How dreadful that would be!

Dreadful indeed. God grant that it may never happen. More terrible
changes of land and water have happened, and are happening still in the
world: but none, I think, could happen which would destroy so much
civilisation and be such a loss to mankind, as that the Thames valley
should become again what it was, geologically speaking, only the other
day, when these gravel banks, over which we are running to Reading, were
being washed out of the chalk cliffs up above at every tide, and rolled
on a beach, as you have seen them rolling still at Ramsgate.

Now here we are at Reading. There is the carriage waiting, and away we
are off home; and when we get home, and have seen everybody and
everything, we will look over our section once more.

But remember, that when you ran through the chalk hills to Reading, you
passed from the bottom of the chalk to the top of it, on to the Thames
gravels, which lie there on the chalk, and on to the London clay, which
lies on the chalk also, with the Thames gravels always over it. So that,
you see, the newest layers, the London clay and the gravels, are lower in
height than the limestone cliffs at Bristol, and much lower than the old
mountain ranges of Devonshire and Wales, though in geological order they
are far higher; and there are whole worlds of strata, rocks and clays,
one on the other, between the Thames gravels and the Devonshire hills.

But how about our moors? They are newer still, you said, than the London
clay, because they lie upon it: and yet they are much higher than we are
here at Reading.

Very well said: so they are, two or three hundred feet higher. But our
part of them was left behind, standing up in banks, while the valley of
the Thames was b