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.
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