1S71.] STOW TAAL-EIVER DIAMOND-GEAVELS. 5 



In the accompanying Map (PI. I.), which shows the Vaal Eiver 

 from the Plaatberg to its junction with the Eeit River, all the 

 localities where tlie diggers are most thickly congregated are in- 

 dicated. 



My friend Mr J. Graham, who has furnished me with the results 

 of some observations he made on the level of the river, found by the 

 aneroid that its fall was exceedingly small. Between Hebron and 

 Klip Drift, a distance, along the course of the river, of more than 

 25 miles, it was only 22 feet. The stream is divided into long level 

 reaches ; and these in most cases are joined by a succession of small 

 rapids. Three of those below Pniel are marked as Kos. 1, 2, and 3, 

 on the map. The sinuosities of the river are very remarkable. 



Whatever may have been the agency that occasioned the vast 

 accumulations of gravel and boulders that we have to treat of, it 

 must have been something more powerful than a current like that 

 of the present Vaal. 



The country to the south of the river consists of immense gently 

 undulating flats, with scarcely any eminences worthy of being called 

 hills. South of the Plaatberg the onh'^ elevation forming a range is 

 between Bult-Fontein and Robinson's ; and this only rises to a height 

 of 400 or 500 feet. 



A large portion of the country to the south of the Vaal is covered, 

 as has been mentioned, with calcareous tufa, hidden in many places 

 by a thin coating of light sandy soil, just sufficient to support a 

 somewhat scanty herbage. Local depressions in the fiats are very 

 common ; and most of these have no outlets to any lower level, al- 

 though the drainage of a large extent of land slopes from ever}- side 

 towards them. In colonial phraseology they are styled " Braak- 

 Pans." The origin of the depressions has yet to be explained ; but 

 the water of the "pans" appears to be due to its accumulation after 

 heavy rains in these hollows. This is again rapidly evaporated in 

 dry seasons, and leaves the soil impregnated with the saline particles 

 dissolved and carried down thither from the higher slopes by the 

 rain-water. The water, from the peculiar formation of the country 

 just alluded to, has no other means of escape ; thus the constant ad- 

 dition during a long course of ages has had such a sterilizing effect 

 that the growth of all vegetation in the central portion, or " pan," 

 is prevented by the extreme brackishness of the soil. Some of these 

 " pans " are of large size — from 2 to 3 miles in length. Du Toit's 

 Pan is one of this description. Between Jacobsdal and the Camp- 

 bell-grounds there are two such salt-pans. About twelve years ago 

 one of these ceased yielding salt, and continued in the same state for 

 ten years ; but during the last two years it has recommenced depo- 

 siting a large quantity of saline matter. 



Occurrence and geological place of the Diamonds. — Diamonds, up to 

 the present time, have been found principally : — 



1st. In an unstratified gravelly drift, containing immense num- 

 bers of huge boulders, with a red, clayey, ferruginous or ochreous 

 matrix. Pniel is an example of this kind. 



2nd. Unstratified gravel, with boulders most irregularly inter- 



