But it may yet
be asked, how has the solid basalt been removed? Geologists
formerly would have brought into play the violent action of some
overwhelming debacle; but in this case such a supposition would
have been quite inadmissible; because, the same step-like plains
with existing sea-shells lying on their surface, which front the
long line of the Patagonian coast, sweep up on each side of the
valley of Santa Cruz. No possible action of any flood could thus
have modelled the land, either within the valley or along the open
coast; and by the formation of such step-like plains or terraces
the valley itself has been hollowed out. Although we know that
there are tides which run within the Narrows of the Strait of
Magellan at the rate of eight knots an hour, yet we must confess
that it makes the head almost giddy to reflect on the number of
years, century after century, which the tides, unaided by a heavy
surf, must have required to have corroded so vast an area and
thickness of solid basaltic lava. Nevertheless, we must believe
that the strata undermined by the waters of this ancient strait
were broken up into huge fragments, and these lying scattered on
the beach were reduced first to smaller blocks, then to pebbles,
and lastly to the most impalpable mud, which the tides drifted far
into the Eastern or Western Ocean.
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