I Have Recently Been Enabled, Through The Apposite
Discovery Of Dr. Kirk, The Companion Of Livingstone, Not Only To Fortify
My conjecture of 1852, but greatly to extend the inferences concerning
the long period of time during which the central
Parts of Africa have
remained in their present condition, save their degradation by ordinary
atmospheric agencies. My view, as given to this Society in 1852, was
mainly founded on the original and admirable geological researches of
Mr. Bain in the colony of the Cape of Good Hope. It was, that, inasmuch
as in the secondary or mesozoic age of geologists, the northern interior
of that country was occupied by great lakes and marshes, as proved by
the fossil reptile discovered by Bain, and named Dicynodon by Owen, such
it has remained for countless ages, even up to the present day. The
succeeding journeys into the interior, of Livingstone, Thornton and
Kirk, Burton and Speke, and Speke and Grant, have all tended to
strengthen me in the belief that Southern Africa has not undergone any
of those great submarine depressions which have so largely affected
Europe, Asia, and America, during the secondary, tertiary, and quasi
modern periods.
"The discovery of Dr. Kirk has confirmed my conclusion. On the banks of
an affluent of the Zambesi, that gentleman collected certain bones,
apparently carried down in watery drifts from inland positions, which
remains have been so fossilized as to have all the appearance of
antiquity which fossils of a tertiary or older age usually present. One
of these is a portion of the vertebral column and sacrum of a buffalo,
undistinguishable from that of the Cape buffalo; another is a fragment
of a crocodile, and another of a water-tortoise, both undistinguishable
from the forms of those animals now living. Together with these, Dr.
Kirk found numerous bones of antelopes and other animals, which, though
in a fossil condition, all belonged, as he assured me, to species now
living in South Africa.
"On the other hand, none of our explorers, including Mr. Bain, who has
diligently worked as a geologist, have detected in the interior any
limestones containing marine fossil remains, which would have proved
that South Africa had, like other regions, been depressed into oceanic
conditions, and re-elevated. On the contrary, in addition to old
granitic and other igneous rocks, all explorers find only either
innumerable undulations of sandstones, schistose, and quartzose rocks,
or such tufaceous and ferruginous deposits as would naturally occur in
countries long occupied by lakes and exuberant jungles, separated from
each other by sandy hills, scarcely any other calcareous rocks being
found except tufas formed by the deposition of landsprings. It is true
that there are marine tertiary formations on the coasts (around the Cape
Colony, near the mouth of the Zambesi opposite Mozambique, and again on
the coasts of Mombas opposite Zanzibar), and that these have been raised
up into low-coast ranges, followed by rocks of igneous origin. But in
penetrating into the true interior, the traveller takes a final leave of
all such formations; and in advancing to the heart of the continent, he
traverses a vast region which, to all appearance, has ever been under
terrestrial and lacustrine conditions only.
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