en exposed to the action of the sea waves, for centuries, perhaps,
before the sands began to cover it. For you find the surface of the
chalk furrowed, worn into deep pits, which are often filled with
sand, and gravel, and rounded lumps of chalk. You may see this for
yourselves, in the topmost layer of any chalk-pit round here. You
may see, even, in some places, the holes which boring shells, such
as work now close to the tide-level, have made in it; all the signs,
in fact, of the chalk having been a rocky sea-beach for ages.

The first bed which you will generally find upon the water-worn
surface of the chalk is a layer of green-sand and green-coated
flints. Among these are met with in many places beds of a great
oyster, now unknown in life. I cannot say whether there are any
here; but at Reading, to the east of Farnham, at Croydon, and under
London, they are abundant. There must have been miles and miles of
oyster-bed at the bottom of that Eocene sea; among the oyster-beds,
beds of a peculiar pebble, which we shall see in our gravel-pit.

They are flints; but very small, dark, often almost black, and quite
round and polished. Compare them with the average flints of the
pit, and you see that while the average flints are fresh from the
chalk, these have plainly been rolled and rounded for years. They
are (except in their dark colour) exactly such shingle as forms the
south-coast beach about Hastings and Brighton. They are the shingle
beaches of the Eocene sea, part of which are preserved under the
London clay. To the north a vast bed of them remains in its
original place, on Blackheath near London; while part, in the
district to the south, which the London clay has not covered, have
been washed away, and carried into our gravel-pit, to mingle with
other flints fresh from the chalk.

I said just now that I had proof that a great tract of the chalk-
hills which are now bare, was once covered with sand and gravel.
Here, in the presence of these dark pebbles, is a proof. But I have
another, and a yet more curious one.

For our gravel-pit, if it be, will possibly yield us another, and a
more curious object. You most of you have seen, I dare say, large
stones, several feet long, taken out of these pits. In the gravels
and sands at Pirbright they are so plentiful that they are quarried
for building-stone. And good building-stone they make; being
exceedingly hard, so that no weather will wear them away. They a