It is therefore probable that these deposits of salt are the remains of the very slightly brackish lakes of antiquity, large portions of which must have been dried out in the general desiccation.

We see an instance in Lake Ngami, which, when low, becomes brackish, and this view seems supported by the fact that the largest quantities of salt have been found in the deepest hollows or lowest valleys, which have no outlet or outgoing gorge; and a fountain, about thirty miles south of the Bamangwato--the temperature of which is upward of 100 Deg .-- while strongly impregnated with pure salt, being on a flat part of the country, is accompanied by no deposit.
When these deposits occur in a flat tufaceous country like the present, a large space is devoid of vegetation, on account of the nitrates dissolving the tufa, and keeping it in a state unfavorable to the growth of plants.
We found a great number of wells in this tufa.

A place called Matlomagan-yana, or the "Links", is quite a chain of these never-failing springs.

As they occasionally become full in seasons when no rain falls, and resemble somewhat in this respect the rivers we have already mentioned, it is probable they receive some water by percolation from the river system in the country beyond.

Among these links we found many families of Bushmen; and, unlike those on the plains of the Kalahari, who are generally of short stature and light yellow color, these were tall, strapping fellows, of dark complexion.