If I Had Space I Could Prove That
South America Was Formerly Here Cut Off By A Strait, Joining
The Atlantic And Pacific Oceans, Like That Of Magellan.
But It May Yet Be Asked, How Has The Solid Basalt Been
Moved?
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 had 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.
With the change in the geological structure of the plains
the character of the landscape likewise altered. While rambling
up some of the narrow and rocky defiles, I could almost
have fancied myself transported back again to the barren
valleys of the island of St. Jago. Among the basaltic cliffs
I found some plants which I had seen nowhere else, but
others I recognised as being wanderers from Tierra del
Fuego. These porous rocks serve as a reservoir for the
scanty rain-water; and consequently on the line where the
igneous and sedimentary formations unite, some small
springs (most rare occurrences in Patagonia) burst forth;
and they could be distinguished at a distance by the
circumscribed patches of bright green herbage.
April 27th. - The bed of the river became rather narrower
and hence the stream more rapid. It here ran at the rate
of six knots an hour. From this cause, and from the many
great angular fragments, tracking the boats became both
dangerous and laborious.
This day I shot a condor. It measured from tip to tip
of the wings, eight and a half feet, and from beak to tail,
four feet. This bird is known to have a wide geographical
range, being found on the west coast of South America,
from the Strait of Magellan along the Cordillera as far as
eight degrees north of the equator. The steep cliff near the
mouth of the Rio Negro is its northern limit on the Patagonian
coast; and they have there wandered about four
hundred miles from the great central line of their habitations
in the Andes.
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