I Said The Rivers Lie On The Highest Part Of The Delta; Not Always The
Highest, But Seldom The Lowest.
There is reason to believe that in the
course of centuries they oscillate from side to side.
For instance,
four miles north of the Rakaia there is a terrace some twelve or
fourteen feet high; the water in the river is nine feet above the top of
this terrace. To the eye of the casual observer there is no perceptible
difference between the levels, still the difference exists and has been
measured. I am no geologist myself, but have been informed of this by
one who is in the Government Survey Office, and upon whose authority I
can rely.
The general opinion is that the Rakaia is now tending rather to the
northern side. A fresh comes down upon a crumbling bank of sand and
loose shingle with incredible force, tearing it away hour by hour in
ravenous bites. In fording the river one crosses now a considerable
stream on the northern side, where four months ago there was hardly any;
while after one has done with the water part of the story, there remains
a large extent of river-bed, in the process of gradually being covered
with cabbage-trees, flax, tussock, Irishman, and other plants and
evergreens; yet after one is once clear of the blankets (so to speak) of
the river-bed, the traces of the river are no fresher on the southern
than on the northern side, even if so fresh.
The plains, at first sight, would appear to have been brought down by
the rivers from the mountains. The stones upon them are all water-worn,
and they are traversed by a great number of old water-courses, all
tending more or less from the mountains to the sea. How, then, are we
to account for the deep and very wide channels cut by the rivers? - for
channels, it may be, more than a mile broad, and flanked on either side
by steep terraces, which, near the mountains, are several feet high? If
the rivers cut these terraces, and made these deep channels, the plains
must have been there already for the rivers to cut them. It must be
remembered that I write without any scientific knowledge.
How, again, are we to account for the repetition of the phenomenon
exhibited by the larger rivers, in every tributary, small or great, from
the glaciers to the sea? They are all as like as pea to pea in
principle, though of course varying in detail. Yet every trifling
watercourse, as it emerges from mountainous to level ground, presents
the same phenomenon, namely, a large gully, far too large for the water
which could ever have come down it, gradually widening out, and then
disappearing. The general opinion here among the reputed cognoscenti
is, that all these gullies were formed in the process of the gradual
upheaval of the island from the sea, and that the plains were originally
sea-bottoms, slowly raised, and still slowly raising themselves.
Doubtless, the rivers brought the stones down, but they were deposited
in the sea.
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