out forty
geographical miles from the nearest part of the gulf called the Zuyder
Zee, and more than twice that distance from the general coast-line. The
present head of the delta of the Nile is about 80 or 90 geographical
miles from the sea; that of the Ganges, as before stated, 220; and that
of the Mississippi about 180, reckoning from the point where the
Atchafalaya branches off to the extremity of the new tongue of land in
the Gulf of Mexico. But the comparative distance between the heads of
deltas and the sea affords no positive data for estimating the relative
magnitude of the alluvial tracts formed by their respective rivers, for
the ramifications depend on many varying and temporary circumstances,
and the area over which they extend does not hold any constant
proportion to the volume of water in the river.

The Rhine therefore has at present three mouths. About two-thirds of its
waters flow to the sea by the Waal, and the remainder is carried partly
to the Zuyder Zee by the Yssel, and partly to the ocean by the Leck. As
the whole coast to the south as far as Ostend, and on the north to the
entrance of the Baltic, has, with few exceptions, from time immemorial,
yielded to the force of the waves, it is evident that the common delta
of the Rhine, Meuse, and Scheldt, for these three rivers may all be
considered as discharging their waters into the same part of the sea,
would, if its advance had not been checked, have become extremely
prominent; and even if it had remained stationary, would long ere this
have projected far beyond the rounded outline of the coast, like that
strip of land already described at the mouth of the Mississippi. But we
find, on the contrary, that the islands which skirt the coast have not
only lessened in size, but in number also, while great bays have been
formed in the interior by incursions of the sea.

In order to explain the incessant advance of the ocean on the shores and
inland country of Holland, M. E. de Beaumont has suggested that there
has in all probability been a general depression or sinking of the land
below its former level over a wide area. Such a change of level would
enable the sea to break through the ancient line of sand-banks and
islands which protected the coast,--would lead to the enlargement of
bays, the formation of new estuaries, and ultimately to the entire
submergence of land. These views appear to be supported by the fact that
several peat-mosses of fresh-water o