86 THE TROPICAL WORLD. 



of retaining its remaining moisture, and few showers can be 

 given to the central and western lands. Thus, while the sea- 

 board gorges of the eastern zone are clad with gigantic forests, 

 and an annual supply of rain there keeps a large number of 

 streams perpetually flowing, Damara Land, the Namaqua 

 country, and the Kalahari, are almost constantly deprived of 

 moving water. 



From these general remarks it might be imagined that regions 

 so scantily supplied with one of the prime necessaries of life 

 could be nothing but a dead and naked waste ; yet, strange to 

 say, even the great Kalahari, extending from the Orange river 

 in the south, lat. 29°, to Lake Ngami in the north, lat. 21°, and 

 from about 24° E. long, to near the west coast, has been called 

 a desert simply because it contains no flowing streams and very 

 little water in wells ; as, far from being destitute of vegetable 

 or animal life, it is covered with grass and a great variety of 

 creeping plants, interspersed with large patches of bushes and 

 even trees. In general, the soil is a light-coloured, soft sand ; 

 but the beds of the ancient rivers contain much alluvial soil, 

 and, as that is baked hard by the burning sun, rain-water stands 

 in pools in some of them for several months in the year. 



The abundance of vegetation on so unpromising a soil may 

 partly be explained by the geological formation of the country ; 

 for as the basin-shape prevails over large tracks, and as the 

 strata on the slopes where most of the rain falls dip in towards 

 the centre, they probably guide water beneath the plains, which 

 are but ill-supplied with moisture from the clouds. 



Another cause, which serves to counteract the want or scarcity 

 of rain, is the admirable foresight of Nature in providing these 

 arid lands with plants suited to their peculiar climate. Thus 

 creepers abound which, having their roots buried far beneath 

 the soil, feel but little the effects of the scorching sun. The 

 number of these which have tuberous roots is very great — a 

 structure evidently intended to supply nutriment and moisture 

 when, during the long droughts, they can be obtained nowhere 

 else. 



One of these blessings to the inhabitants of the desert is 

 the Leroshua, a small plant with linear leaves, and a stalk not 

 thicker than a crow's quill ; but on digging down a foot or 



I 



