t its present
very simple literal outline. This was the length to which I had come.

The trap rocks, which now constitute the "filling up" of the great
valley, were always a puzzle to me till favored with Sir Roderick
Murchison's explanation of the original form of the continent, for then
I could see clearly why these trap rocks, which still lie in a perfectly
horizontal position on extensive areas, held in their substance angular
fragments, containing algae of the old schists, which form the bottom
of the original lacustrine basin: the traps, in bursting through, had
broken them off and preserved them. There are, besides, ranges of hills
in the central parts, composed of clay and sandstone schists, with
the ripple mark distinct, in which no fossils appear; but as they are
usually tilted away from the masses of horizontal trap, it is probable
that they too were a portion of the original bottom, and fossils may yet
be found in them.*

* After dwelling upon the geological structure of the Cape
Colony as developed by Mr. A. Bain, and the existence in very
remote periods of lacustrine conditions in the central part of
South Africa, as proved by fresh-water and terrestrial
fossils, Sir Roderick Murchison thus writes:

"Such as South Africa is now, such have been her main features
during countless past ages anterior to the creation of the
human race; for the old rocks which form her outer fringe
unquestionably circled round an interior marshy or lacustrine
country, in which the Dicynodon flourished, at a time when not
a single animal was similar to any living thing which now
inhabits the surface of our globe. The present central and
meridian zone of waters, whether lakes or marshes, extending
from Lake Tchad to Lake 'Ngami, with hippopotami on their
banks, are therefore but the great modern residual
geographical phenomena of those of a mesozoic age. The
differences, however, between the geological past of Africa
and her present state are enormous. Since that primeval time,
the lands have been much elevated above the sea-level--
eruptive rocks piercing in parts through them; deep rents and
defiles have been suddenly formed in the subtending ridges
through which some rivers escape outward.

"Travelers will eventually ascertain whether the basin-shaped
structure, which is here announced as having been the great
feature of the most ancient, as it i