e finer particles, they had not generally
strength to move these sandstone blocks, but let them drop through,
and remain upon the freshly-bared floor of chalk, as the only relics
of a tertiary land long since swept away; while some were carried
off, possibly by icebergs, as far as Pirbright, and dropped, as the
icebergs melted, both there, at Dogmersfield, and also, though few
and small, in Eversley and the neighbourhood.

But how came these tertiary sandstones to be so very hard, while the
strata around them are so soft?

Ladies and gentlemen, I know no more than you. Experience seems to
say that stone will not harden into that sugary crystalline state,
save under the influence of great heat: but I do not know how the
heat should have got to that layer in particular. Possibly there
may have been eruptions of steam, of boiling water holding silex
(flint) in solution--a very rare occurrence: but something similar
is still going on in the famous Geysers or boiling springs of
Iceland. However, I have no proof that this was the cause. I
suppose we shall find out some day how it happened; for we must
never despair of finding out anything which depends on facts.

Part of the town of Odiham, and of North Warnborough, stands, I
believe, upon these lower beds, which are called by geologists the
Woolwich and Reading beds, and the Plastic clays, from the good
brick earth which is so often found among them. But as soon as you
get to Hook Common, and to Dogmersfield Park, you enter on a fresh
deposit; the great bed of the London clay.

I give you a rough section, from a deep well at Dogmersfield House;
from which you may see how steeply the chalk dips down here under
the clay, so that Odiham stands, as it were, on the chalk beach of
the clay sea.

In boring that well there were pierced:

Forty feet of the upper sands (the Bagshot sands), of which I shall
speak presently.

Three hundred and thirty feet of London clay.

Then about forty feet of mottled clays and sands.

Whether the chalk was then reached, I do not know. It must have
been close below. But these mottled clays and sands abound in water
(being indeed the layer which supplies the great breweries in
London, and those soda-water bottles on dumb-waiters which squirt in
Trafalgar Square); and (I suppose) the water being reached, the
boring ceased.

Now, this great bed of London clay, even more than the sands below
it, deserves the title of a new creation