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the momentum gained hy the rapid descent seemed to urge
the bird upwards, with the even and steady movement of a
paper kite. In the case of any bird soaring, its motion must
be sufficiently rapid, so that the action of the inclined surface
of its body on the atmosphere, may counterbalance its
gravity. The force to keep up the momentum of a body
moving in a horizontal plane in that fluid (in which there is
so little friction) cannot be great, and this force is all that is
wanted. The movement of the neck and body of the condor,
we must suppose, is sufficient for this. However this
may be, it is truly wonderful and beautiful to see so great a
bird, hour after hour, without any apparent exertion, wheeling
and gliding over mountain and river.
A p r i i . 2 9 t h .—From some high land we hailed with joy
the white summits of the Cordillera, as they were seen occasionally
peeping through their dusky envelope of clouds.
During the few succeeding days, we continued to get on
slowly, for we found the river-course very tortuous, and
strewed with immense fragments of various ancient slaty
rocks, and of granite. The plain bordering the valley had
here attained an elevation of about 1100 feet, and its
character was much altered. The well-rounded pebbles of
porphyry were in this part mingled with many immense
angular fragments of basalt and of the rocks above mentioned.
The first of these erratic blocks which I noticed,
was sixty-seven miles distant from the nearest mountain;
another which had been transported to rather a less distance,
measured five yards square, and projected five feet
above the gravel. Its edges were so angular, and its size
so great, that I at first mistook it for a rock in situ, and
took out my compass to observe the direction of its cleavage.
The plains here were not quite so level as those nearer the
coast, but yet, they betrayed little signs of any violent action.
Under these circumstances, it would be difficult, as it appears
to me, to explain this phenomenon on any theory, excepting
through that of transport by ice while the country was under
water. But this is a subject to which I shall again recur.
During the two last days we met with signs of horses, and
with sevei-al small articles which had belonged to the Indians,
—such as parts of a mantle and a bunch of ostrich feathers—
but they appeared to have been lying long on the ground.
Between the place where the Indians had so lately crossed
the river and this neighbourhood, though so many miles
apart, the country appears to be quite unfrequented. At
first, considering the abundance of the guanacoes, I was
surprised at th is; but it is explained by the stony nature of
the plains, which would soon disable an unshod horse from
taking part in the chase. Nevertheless, in two places in this
very central region, I found small heaps of stones, which I
do not think could have been accidentally thrown together.
They were placed on points, projecting over the edge of the
highest lava cliff, and they resembled, but on a small scale,
those near Port Desire.
M a y 4 t i i .— Captain FitzRoy determined to take the
boats no higher. The river had a winding course, and was
very rapid; and the appearance of the country offered no
temptation to proceed any further. Fvery where we met
with the same productions, and the same dreary landscape.
We were now one hundred and forty miles distant from
the Atlantic, and about sixty from the nearest arm of the
Pacific. The valley in this upper part expanded into a wide
basin, bounded on the north and south by the basaltic platforms,
and fronted by the long range of the snow-clad
Cordillera. But we viewed these grand mountains with regret,
for we were obliged to imagine their form and nature,
instead of standing, as we had hoped, on their crest, and
looking down on the plain below. Besides the useless loss
of time which an attempt to ascend any higher would have
cost us, we had already been for some days on half allowance
of bread. This, although really enough for any reasonable
men, was, after our hard day’s march, rather scanty food.
Let those alone who have never tried it, exclaim about the
comfort of a light stomach and an easy digestion.
5 t h .—.Before sunrise we commenced our descent. We
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