rigin now occur under the level of
the sea, especially on the site of the Zuyder Zee and Lake Flevo,
presently to be mentioned. Several excavations also made for wells at
Utrecht, Amsterdam, and Rotterdam have proved, that below the level of
the ocean, the soil near the coast consists of alternations of sand with
marine shells, and beds of peat and clay, which have been traced to the
depth of fifty feet and upwards.[443]

I have said that the coast to the south as far as Ostend has given way.
This statement may at first seem opposed to the fact, that the tract
between Antwerp and Nieuport, shaded black in the annexed map (fig. 38),
although now dry land, and supporting a large population, has, within
the historical period, been covered with the sea. This region, however,
consisted, in the time of the Romans, of woods, marshes, and
peat-mosses, protected from the ocean by a chain of sandy dunes, which
were afterwards broken through during storms, especially in the fifth
century. The waters of the sea during these irruptions threw down upon
the barren peat a horizontal bed of fertile clay, which is in some
places three yards thick, full of recent shells and works of art. The
inhabitants, by the aid of embankments and the sand dunes of the coast,
have succeeded, although not without frequent disasters, in defending
the soil thus raised by the marine deposit.[444]

_Inroads of the Sea in Holland._--If we pass to the northward of the
territory just alluded to, and cross the Scheldt, we find that between
the fourteenth and eighteenth centuries parts of the islands Walcheren
and Beveland were swept away, and several populous districts of Kadzand,
losses which far more than counterbalance the gain of land caused by the
sanding up of some pre-existing creeks. In 1658 the Island Orisant was
annihilated. One of the most memorable inroads of the sea occurred in
1421, when the tide, pouring into the mouth of the united Meuse and
Waal, burst through a dam in the district between Dort and
Gertrudenberg, and overflowed seventy-two villages, forming a large
sheet of water called the Bies Bosch. (See map, fig. 38.) Thirty-five of
the villages were irretrievably lost, and no vestige, even of their
ruins, was afterwards seen. The rest were redeemed, and the site of the
others, though still very generally represented on maps as an estuary,
has in fact been gradually filled up by alluvial deposits, and had
become in 1835, as I was informed