we know that the mass could not have been accumulated on
the beach itself. At the present time, part of the bed is
daily washed by the tide, while another part has been raised
a few feet above the level of the sea. Hence we may infer,
that the elevation has here been trifling, since the period
when the mammaha, now extinct, were living. This conclusion
is in harmony with several other considerations (such
as the recent character of the beds underlying the Pampas
deposit), but which I have not space in this work to
enter on.
From the general structure of the coast of this part of
South America, we are compelled to believe, that the changes
of level have all (at least of late) been in one direction, and
that they have been very gradual. If, then, we look back
to the period when these quadrupeds lived, the land probably
stood at a level, less elevated only by a few fathoms
than at present. Therefore, its general configuration since
that epoch cannot have been greatly m o d i f i e d ; a conclusion
wliich certainly would be drawn from the close similarity in
every respect, between the shells now living in the bay (as
well as in the case of the one terrestrial species) with those
which formerly lived there.
The surrounding country, as may have been gathered from
this journal, is of a very desert character. Trees nowhere
occur, and only a few bushes, which are chiefly confined to
depressions among the sand-hillocks, or to the borders of the
saline marshes. Here, then, is an apparent difSculty: we
have the strongest evidence that there has occurred no great
physical change to modify the features of the country, yet
in former days, numerous large animals were supported on
the plains now covered by a thin and scanty vegetation.
That large animals require a luxuriant vegetation, has been
a general assumption, which has passed from one work to
another. I do not hesitate, however, to say that it is completely
false ; and that it has vitiated the reasoning of geologists,
on some points of great interest in the ancient history
of the world. The prejudice has probably been derived
from India, and the Indian islands, where troops of
elephants, noble forests, and impenetrable jungles, are
associated together in every account. If, on the other hand,
we refer to any work of travels through the southern parts
of Africa, we shall find allusions in almost every page either
to the desert character of the country, or to the numbers
of large animals inhabiting it. The same thing is rendered
evident by the many sketches which have been published of
various parts of the interior. When the Beagle was at Cape
Town, I rode a few leagues into the country, which at least
was sufficient to render that which I had read more fully
intelligible.
Dr. Andrew Smith, who, at the head of his adventurous
party, has so lately succeeded in passing the Tropic of
Capricorn, informs me that, taking into consideration the
whole of the southern part of Africa, there can be no doubt of
its being sterile country. On the southern and south-eastern
coasts there are some fine forests, but with these exceptions,
the traveller may pass, for days together, through open
plains, covered by a poor and scanty vegetation. It is difficult
to convey any accurate idea of degrees of comparative
fertility; but it may be safely said, that the amount of
vegetation supported at any one time* by Great Britain,
exceeds, perhaps even tenfold, the quantity on an equal
area, in the interior parts of Southern Africa. The fact that
bullock-waggons can travel in any direction, excepting near
the coast, without more than occasionally half an hour’s
delay, gives, perhaps, a more definite notion of its scantiness.
Now if we look to the animals inhabiting these wide
plains, we shall find their numbers extraordinarily great,
and their bulk immense. We must enumerate the elephant,
three species of rhinoceros, and as Dr. Smith is convinced
two others also, the hippopotamus, giraffe, the bos caffer—as
large as a full-grown bull, and the elan—but little less, two
* I m e a n b y th is to e x c lu d e tlie to ta l am o u n t, w h ic h m ay h a v e b een
successiv(:ly priKliicci] iind consiniK’d d u r in g a g iv en p e rio d .
Ii 2