be true, if you went south-
east from here toward the Hind Head. The chalk lies on the top of
the sands of Crooksbury Hill, and the clays of Holt Forest; but it
dips underneath the sands of Shapley Heath, and the clays of
Dogmersfield, and reappears from underneath them again at Reading.

Thus you at Odiham stand on the edge of a chalk basin; of what was
once a sea, or estuary, with shores of chalk, which begins at the
foot of the High Clere Hills, and runs eastward, widening as it
goes, past London, into the Eastern Sea. Everywhere under this
great basin is the floor of chalk, covered with clays and sands,
which, for certain reasons, are called by geologists Tertiary
strata.

But what has this to do with a gravel-pit?

This first. That all the flints in this pit have come out of the
chalk. They are coloured, most of them, with iron, which has turned
them brown; but they are exactly the same flints as those gray ones
in the chalk-pit on the other side of the town.

How do I know that?

I think our own eyes will prove it: they are the same shapes, and
of the same substance; but as a still surer proof, we find exactly
the same fossils in them; sponges, choanites (which were something
like our modern sea-anemones), corals, and "shepherds' crowns" as
the boys call the fossil sea-urchins. The species of all these, and
of other fossils, in the chalk-pit and in the gravel-pit, are
absolutely identical. The natural conclusion is, then, that the
gravel has been formed from the washings of the chalk. The white
lime of the chalk has been carried away in water by some flood or
floods; the heavier flints have been left behind.

Stop now one moment, and think. You all know how very few flints
there are in the chalk-pit, in proportion to the mass of chalk. You
all know what vast gravel-beds cover the country to the north, and
often to the thickness of many feet. Try and conceive, then, what a
much more vast mass of chalk must have been washed away, to leave
that vast mass of gravel behind it.--Conceive? It is past
conception. I will but give you two hints as to its probable size.

The chalk to the eastward, between here and Farnham, is a far
narrower and shallower band than anywhere else in England. Its
narrowest point is, I believe, beneath the bishop's palace at
Farnham, where it may be a hundred feet thick, instead of several
hundred, as it usually is in other parts of England. The cause of
this is, that t