nd were restricted to the
stratum of hardened mould.

I carried on my researches in this--what I may term the
chronological--direction, in connexion with the old-coast line, which,
as I have already said, is finely developed in the neighbourhood of
Cromarty on both sides of the Firth, and represented along the
precipices of the Sutors by its line of deep caves, into which the sea
never now enters. And it, too, pressed upon me the fact of the amazing
antiquity of the globe. I found that the caves hollowed by the
surf--when the sea stood from fifteen to five-and-twenty feet above its
present level, or, as I should perhaps rather say, when the land sat
that much lower--were deeper, on the average, by about one-third, than
those caves of the present coast-line that are still in the course of
being hollowed by the waves. And yet the waves have been breaking
against the present coast-line during the whole of the historic period.
The ancient wall of Antoninus, which stretched between the Firths of
Forth and Clyde, was built at its terminations with reference to the
existing levels; and ere Caesar landed in Britain, St. Michael's Mount
was connected with the mainland, as now, by a narrow neck of beach laid
bare by the ebb, across which, according to Diodorus Siculus, the
Cornish miners used to drive, at low water, their carts laden with tin.
If the sea has stood for two thousand six hundred years against the
present coast-line--and no geologist would fix his estimate of the term
lower--then must it have stood against the old line, ere it could have
excavated caves one-third deeper than the modern ones, three thousand
nine hundred years. And both sums united more than exhaust the Hebrew
chronology. Yet what a mere beginning of geologic history does not the
epoch of the old coast-line form! It is but a starting-point from the
recent period. Not a single shell seems to have become extinct during
the last six thousand years. The organisms which I found deeply embedded
in the soil beneath the old coast-line were exactly those which still
live in our seas; and I have been since told by Mr. Smith of Jordanhill,
one of our highest authorities on the subject, that he detected only
three shells of the period with which he was not familiar as existing
forms, and that he subsequently met with all three, in his dredging
expeditions, still alive. The six thousand years of human history form
but a portion of the geologic day that is passing o