in the morning we ascended the Sierra de las Animas. By
the aid of the rising sun the scenery was almost picturesque.
To the westward the view extended over an immense level
plain as far as the mount, at Monte Video, and to the eastward,
over the mammillated country of Maldonado. On the
summit of the mountain there were several small heaps of
stones, which evidently had lain there for many years. My
companion assured me that they were the work of the
Indians in the old time. The heaps were similar, but on a
much smaller scale, to those so commonly found on the
mountains of Wales. The desire to signalize any event, on
the highest point of the neighbouring land, seems an universal
passion with mankind. At the present day, not a
sino-le Indian, either civilized or wild, exists in this part of
the province; nor am I aware that the former inhabitants
have left behind them any more permanent records, than
these insignificant piles on the summit of the Sierra de las
Animas.
The geological structure of the country is very simple.
On the crest of every hill, granitic or ancient schistose rocks
protrude; the intervening spaces being concealed by a great
thickness of a red argillaceous earth. This at first sight
would he mistaken for ordinary detritus; but on closer examination
it is found to contain small concretionary balls of
a friable limestone or marl, and to possess other peculiar
characters. It extends over the whole province, and in
some places is very remarkable, from containing the remains
of several great extinct animals. This red earthy substance
is part of the formation which composes those immense
plains of Buenos Ayres, denominated the Pampas. For its
origin, we must look to a period when the estuary of the
Plata, occupying far wider limits, covered all the surrounding
low countries with its brackish waters. Signs oi the
gradual elevation of the land can in many places be discovered
on the shores of the river; and it probable that
the red earthy mass is, geologically speaking, of no very
ancient date.
The general, and almost entire absence of trees in
Banda Oriental is remarkable. Some of the rocky hills are
partly covered by thickets, and on the banks of the larger
streams, especially to the northward of the Las Minas,
willow-trees are not uncommon. Near the Arroyo Tapes I
heard of a wood of palms ; and one of these trees, of considerable
size, I saw near the Pan de Azúcar, in lat. 35°.
These, and the trees planted by the Spaniards, offer the
only exceptions to the general scarcity of wood. Among
the introduced kinds may bg enumerated poplars, olives,
peach, and other fruit-trees: the peaches succeed so well,
that they afford the main supply of firewood to the city
of Buenos Ayres. Extremely level countries, such as
the Pampas, seldom appear favourable to the growth of
trees. This may possibly be attributed either to the force
of the winds, or the kind of drainage. In the nature of
the land, however, around Maldonado, no such reason is
apparent; the rocky mountains afford protected situations,
enjoying various kinds of soil; streamlets of water are common
at the bottoms of nearly every valley; and the clayey
nature of the earth seems adapted to retain moisture. It
has been inferred with much probability, that the presence
of woodland is determined by the annual amount of moisture;
yet in this province abundant and heavy rain falls during the
winter; and the summer, though dry, is not so in any excessive
degree.# We see nearly the whole of Australia covered
by lofty trees, yet that country possesses a far more arid
climate. Hence we must look to some other cause. The
trees of Brazil cannot travel so far southward, on account of
the colder climate; nor does there exist any other wooded
country whence a migration could take place: we are therefore
driven to the conclusion that herbaceous plants, instead
of trees, were created to occupy that wide area, which
within a period not very remote, has been raised above the
waters of the sea.