116 Rev. S. S. Donian — Geology of Basutoland. 



a marble up to masses two feet or more in diameter. The edges of the 

 rent into which the molten dolerite has been injected are as clean-cut 

 and straight as if laid out artificially. Small displacements of the 

 neighbouring strata are characteristic features of these dykes. Occasional 

 enclosures of sandstone occur in dykes, but they rarely exceed three 

 feet in thickness. From observations made at widely separated places, 

 I am convinced that these dykes and sheets were intruded into the 

 lavas long after volcanic action had ceased, at least from the main 

 centres of eruption, but before the earth-movements to which the 

 country largely owes its present configuration had begun. 



Recent and superficial deposits cover the low grounds, and consist 

 of stratified clays, sands, and gravels. The pebbles of the gravels 

 consist of fragments from all the Stormberg rocks. In many places 

 these deposits are more than 30 feet thick. The rivers in the course 

 of ages have cut their waj' through them, and, as they are loose and 

 easily removed, the amount swept away by every storm is considerable. 

 Large masses fall from the banks during the rains, with the result 

 that a small stream becomes in a short time a huge gaping donga. 

 These dongas everywhere intersect the country, and are a positive 

 danger, especially during the rainy season. The destruction of the 

 wood and bush of the country, together with the increase of cattle 

 that eat oif the grass, has powerfully assisted the formation of these 

 dongas. They not only reduce the area of arable land, but also drain 

 off the water and disfigure the country. If nothing be done to check 

 their formation they will render the water problem a very serious one 

 at no distant date. When the first missionaries came to Basutoland 

 about 75 years ago multitudes of these dongas did not exist. A deep 

 donga near Morija was forty years ago a small stream that one could 

 step across; now it is a trench 15 feet deep and more than 20 feet 

 wide. It is a pity that the Basuto cannot be induced to plant trees 

 more extensively. They would at least do something towards checking- 

 denudation, besides being useful as fuel in a country where such 

 a commodity is exceedingly scarce. The Government is trying to 

 induce the natives to plant by the gift of trees, and they are slowly 

 waking up to the necessity of it. 



The most interesting of the superficial deposits are the sand dunes 

 on Thaba Bosin mountain. They occupy the south-eastern portion of 

 the plateau, and travel east or west according to the direction and 

 strength of prevailing winds. These sand dunes are formed of dis- 

 integrated Cave Sandstone, the grains being chiefly quartz and felspar. 

 They cover many acres in extent. Thaba Bosin is the necropolis of 

 the Basuto chiefs, and every paramount chief, besides many sons and 

 brothers of the ruling chiefs, have been buried there. The sand-hills 

 have partially covered up the graves and appear to be slowly travelling 

 towards the east, as some of the graves formerly hidden are now 

 exposed. They never approach close to the precipitous edge of the 

 plateau, as apparently the updraught of the wind in rushing round 

 and over the plateau prevents the sand from falling over the precipice. 

 They are also beautifully ripple-marked by the wind, and some of them 

 are quite 20 feet in height. Not far from Morija thei'e is the basin of 

 an old lake, just as there are many such prehistoric lake basins over 



