A little soil
lying on calcareous tufa, over a tract of several hundreds of miles,
supports a vegetation of fine sweet short grass, and mopane and baobab trees.
On several parts of this we found large salt-pans, one of which,
Ntwetwe, is fifteen miles broad and one hundred long.
The latitude might have been taken on its horizon as well as upon the sea.
Although these curious spots seem perfectly level, all those in this direction
have a gentle slope to the northeast: thither the rain-water,
which sometimes covers them, gently gravitates. This, it may be recollected,
is the direction of the Zouga. The salt dissolved in the water
has by this means all been transferred to one pan in that direction,
named Chuantsa; on it we see a cake of salt and lime an inch and a half thick.
All the others have an efflorescence of lime and one of the nitrates only,
and some are covered thickly with shells. These shells are identical
with those of the mollusca of Lake Ngami and the Zouga.
There are three varieties, spiral, univalve, and bivalve.
In every salt-pan in the country there is a spring of water on one side.
I can remember no exception to this rule. The water of these springs
is brackish, and contains the nitrate of soda. In one instance
there are two springs, and one more saltish than the other.
If this supply came from beds of rock salt the water would not be drinkable,
as it generally is, and in some instances, where the salt contained in the pan
in which these springs appear has been removed by human agency,
no fresh deposit occurs.
