92 SPRINGS.— BUSHMEN. 



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 ot 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. 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 brack- 

 ish, and this view seems supported by the fact that the largest 

 quantities of salt have been found in the deepest hollows or low- 

 est valleys, which have no outlet or outgoing gorge ; and a fount- 

 ain, about thirty miles south of the Bamangwato — the temperature 

 of which is upward of 100° — 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 Bush- 

 men ; 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. Heat alone does not pro- 

 duce blackness of skin, but heat with moisture seems to insure 

 the deepest hue. 



One of these Bushmen, named Shobo, consented to be our 



