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.

As a proof—­some of you may recollect, when the South-Western Railway was in making, seeing shells—­some of them large and handsome ones—­Nautili, taken out of the London clay cutting near Winchfield.

Nautili similar to them (but not the same) are now only found in the hottest parts of the Indian seas; and what is more, not one of those shells is the same as the shells you find in the chalk.  Throughout this great bed of London clay, the shells, the remains of plants and animals, are altogether a new creation.  If you look carefully at the London clay shells, you will be struck with their general likeness to fresh East Indian shells; and rightly so.  They do approach our modern live shells in form, far more than any which preceded them; and indeed, a few of the London clay shells exist still in foreign seas; in the beds, again, above the clay, you will meet with still more species which are yet alive; while in the chalk, and below the chalk, you never meet, I believe, with a single recent shell.  It is for this reason that the London clay is said to be Eocene, that is, the dawn of the new creation.

The chalk, I told you, seems to have been deposited at the bottom of a still and deep ocean.  But the London clay, we shall find, was deposited in a comparatively shallow sea, least in depth toward High Clere on the west, and deepening towards London and the mouth of the Thames.

For not only is the clay deeper as you travel eastward, but—­and this is a matter to which geologists attach great importance—­the character of the shells differs in different parts of the clay.

You must know that certain sorts of shells live in deep water, and certain in shallow.  You may prove this to yourselves, on a small scale, whenever you go to the seaside.  You will find that the shell which crawl on the rocks about high-water mark are different from those which you find at low-tide mark; and those again different from the shells which are brought up by the oyster-dredgers from the sea outside.  Now, the lower part of the clay, near here, contains shallow-water shells:  but if you went forty miles to the eastward, you would find in the corresponding lower beds of the clay, deep-water shells, and far above them, shallow-water shells such as you find here:  a fact which shows plainly that this end of the clay sea was shallowest, and therefore first filled up.