e all the rocks and
hills that stand like islands, so that we are justified in assuming the
area as at least 100,000 square miles of this basaltic sea.

The molten mass seems to have flowed over in successive waves, and the
top of each wave was covered with a dark vitreous scum carrying scoriae
with angular fragments. This scum marks each successive overflow, as a
stratum from twelve to eighteen inches or more in thickness. In one part
sixty-two strata are revealed, but at the Victoria Falls (which are
simply a rent) the basaltic rock is stratified as far as our eyes could
see down the depth of 310 feet. This extensive sea of lava was probably
sub-aerial, because bubbles often appear as coming out of the rock into
the vitreous scum on the surface of each wave: in some cases they have
broken and left circular rings with raised edges, peculiar to any
boiling viscous fluid. In many cases they have cooled as round pustules,
as if a bullet were enclosed; on breaking them the internal surface is
covered with a crop of beautiful crystals of silver with their heads all
directed to the centre of the bubble, which otherwise is empty.

These bubbles in stone may be observed in the bed of the Kuruman River,
eight or ten miles north of the village; and the mountain called
"Amhan," west-north-west of the village, has all the appearance of
having been an orifice through which the basalt boiled up as water or
mud does in a geyser.

The black basaltic mountains on the east of the Bamangwato, formerly
called the Bakaa, furnish further evidence of the igneous eruptions
being sub-aerial, for the basalt itself is columnar at many points, and
at other points the tops of the huge crystals appear in groups, and the
apices not flattened, as would have been the case had they been
developed under the enormous pressure of an ocean. A few miles on their
south a hot salt fountain boils forth and tells of interior heat.
Another, far to the south-east, and of fresh water, tells the same tale.

Subsequently to the period of gigantic volcanic action, the outflow of
fresh lime-water from the bowels of the earth seems to have been
extremely large. The land now so dry that one might wander in various
directions (especially westwards, to the Kalahari), and perish for lack
of the precious fluid as certainly as if he were in the interior of
Australia, was once bisected in all directions by flowing streams and
great rivers, whose course was mainly to the so