Mr. Gill told me he
had been employed professionally to examine one: he found the
passage low, narrow, crooked, and not of uniform breadth, but of
very considerable length. Is it not most wonderful that men should
have attempted such operations, without the use of iron or
gunpowder? Mr. Gill also mentioned to me a most interesting, and,
as far as I am aware, quite unparalleled case, of a subterranean
disturbance having changed the drainage of a country. Travelling
from Casma to Huaraz (not very far distant from Lima), he found a
plain covered with ruins and marks of ancient cultivation but now
quite barren. Near it was the dry course of a considerable river,
whence the water for irrigation had formerly been conducted. There
was nothing in the appearance of the watercourse to indicate that
the river had not flowed there a few years previously; in some
parts, beds of sand and gravel were spread out; in others, the
solid rock had been worn into a broad channel, which in one spot
was about 40 yards in breadth and 8 feet deep. It is self-evident
that a person following up the course of a stream will always
ascend at a greater or less inclination: Mr. Gill, therefore, was
much astonished, when walking up the bed of this ancient river, to
find himself suddenly going down hill.
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