erhaps the most remarkable case is
that of the Mississippi (Fig. 36), the mouths of which project into the
sea like a hand, or like the petals of a flower. For miles the mud is
too soft to support trees, but is covered by sedges (Miegea); the banks
of mud gradually become too soft and mobile even for them. The pilots
who navigate ships up the river live in frail houses resting on planks,
and kept in place by anchors. Still further, and the banks of the
Mississippi, if banks they can be called, are mere strips of reddish
mud, intersected from time to time by transverse streams of water, which
gradually separate them into patches. These become more and more
liquid, until the land, river, and sea merge imperceptibly into one
another. The river is so muddy that it might almost be called land, and
the mud so saturated by water that it might well be called sea, so that
one can hardly say whether a given spot is on the continent, in the
river, or on the open ocean.

[Illustration: Fig. 36.]

FOOTNOTES:

[48] Leyden.

[49] Dr. Hudson, Address to the Microscopical Society, 1889.

[50] F. Davors.

[51] Ruskin.

CHAPTER VIII

RIVERS AND LAKES

ON THE DIRECTIONS OF RIVERS

In the last chapter I have alluded to the wanderings of rivers within
the limits of their own valleys; we have now to consider the causes
which have determined the directions of the valleys themselves.

If a tract of country were raised up in the form of a boss or dome, the
rain which fell on it would partly sink in, partly run away to the lower
ground. The least inequality in the surface would determine the first
directions of the streams, which would carry down any loose material,
and thus form little channels, which would be gradually deepened and
enlarged. It is as difficult for a river as for a man to get out of a
groove.

In such a case the rivers would tend to radiate with more or less
regularity from the centre or axis of the dome, as, for instance, in our
English lake district (Fig. 37). Derwent Water, Thirlmere, Coniston
Water, and Windermere, run approximately N. and S.; Crummock Water,
Loweswater, and Buttermere N.W. by S.E.; Waste Water, Ullswater, and
Hawes Water N.E. by S.W.; while Ennerdale Water lies nearly E. by W. Can
we account in any way, and if so how, for these varied directions?

The mountains of Cumberland and Westmoreland form a more or less oval
boss, the axis of which, though not straight, runs practically fro