ircumscribed; natural and
artificial barriers having given away, one after another; and many
hundred thousand human beings having perished in the waves.

_Changes in the arms of the Rhine._--The Rhine, after flowing from the
Grison Alps, copiously charged with sediment, first purifies itself in
the Lake of Constance, where a large delta is formed; then swelled by
the Aar and numerous other tributaries, it flows for more than six
hundred miles towards the north; when, entering a low tract, it divides
into two arms, about ten miles northeast of Cleves,--a point which must
therefore be considered the head of its delta. (See[A], map, fig. 8.)
In speaking of the delta, I do not mean to assume that all that part of
Holland which is comprised within the several arms of the Rhine can be
called a delta in the strictest sense of the term; because some portion
of the country thus circumscribed, as, for example, a part of Gelderland
and Utrecht, consists of strata which may have been deposited in the sea
before the Rhine existed. These older tracts may either have been raised
like the Ullah Bund in Cutch, during the period when the sediment of
the Rhine was converting a part of the sea into land, or they may have
constituted islands previously.

[Illustration: Fig. 38.

The dark tint between Antwerp and Nieuport, represents part of the
Netherlands which was land in the time of the Romans, then overflowed by
the sea before and during the 5th century, and afterwards reconverted
into land.]

When the river divides north of Cleves, the left arm takes the name of
the Waal; and the right, retaining that of the Rhine, is connected, a
little farther to the north, by an artificial canal with the river
Yssel. The Rhine then flowing westward divides again southeast of
Utrecht, and from this point it takes the name of the Leck, a name which
was given to distinguish it from the northern arm called the old Rhine,
which was sanded up until the year 1825, when a channel was cut for it,
by which it now enters the sea at Catwyck. It is common, in all great
deltas, that the principal channels of discharge should shift from time
to time, but in Holland so many magnificent canals have been
constructed, and have so diverted, from time to time, the course of the
waters, that the geographical changes in this delta are endless, and
their history, since the Roman era, forms a complicated topic of
antiquarian research. The present head of the delta is ab