4 PROCEEDINGS OE THE GEOLOGICAL SOCIETY. [NoV, 8, 



the north bank of the Orange Eiver, between Bethnlie and Jagcr s 

 Eontein. The sandstones continue beyond the shales (just as we 

 find them on the southern or Great- Winterberg boundary of the 

 same basin), and are visible in the ridges in the direction of Albania, 

 to the north, and of Hopetowu, to the south of the same river. 



At a drift (ford) on the Rcit Eiver, a short distance beyond Jager's 

 Fontein, a mass of rock, which has been termed " clay-slate," makes 

 its appearance. It is of a dark blue slate-colour, and is said to 

 break with a slat}^ fracture. It is possible that this may be a schist 

 more ancient and indurated than the shales of the Stormberg for- 

 mation. Beyond this the greater part of the country is covered with 

 calcareous tufa, on which in some places is a reddish sandy soil, 

 about 2 feet thick. The ground is traversed by numerous dykes, 

 and by other slight ridges which seem to be composed of metamor- 

 phic rocks. On a near approach to the Yaal River the direction of 

 these ridges can be easily traced ; and they all appear to trend 

 E.S.E.-W.jN^.W. In many places quartz-reefs run parallel with the 

 dykes, their thickness varying from a few inches to 15 or 16 feet. 

 No satisfactory conclusion, however, can be arrived at with regard 

 to the basement rocks which intervene between Jager's Fonteiu 

 and Pniel, except that none equivalent to those met with in the 

 upper portion of the Stormberg-basin are to be found there. This part 

 of the country, therefore, in all probability formed a portion of the 

 northern or north-eastern boundary of the great sandstone and shale- 

 system of the Stormberg. (See the paper by Mr. Stow, read before 

 the Geol. Soc. Dec. 7, 1870, Q. J. G. S. vol. xxvii. p. 523.) 



The immense extent of the diamond-deposits seems to be most 

 clearly proved by the widely separated localities in which they have 

 been found (see Map, PL I.). Taking Pniel as a central point, we 

 find that they have been discovered (July 1871) not onl}'- at Jager's 

 Fontein, a place nearly 96 miles on the southern side of the Vaal, 

 but also at Mamusa, 75 miles beyond it. At this latter place a 

 diamond upwards of 70 carats in weight was picked up on the sur- 

 face. How much further these deposits may extend in the same 

 direction is not known ; but even this distance gives a breadth of 

 171 miles. The diamond-bearing country already ascertained 

 stretches down the Yaal River for a distance of 110 miles, to a spot 

 considerably below its junction with the Nu Gariep, or Orange River ; 

 whilst, above Pniel, diamonds have been found at a considerable 

 number of places as far as Bloemhof, 102 miles further up the stream ; 

 and the last reports (July 1871) state that diamonds have been 

 discovered at least 100 miles nearer the sources of the river, a dis- 

 tance of quite 312 miles from the most southern point previously 

 mentioned. 



hypothesis advanced in the ' Greological Magazine,' will be found on comparing 

 these papers. I must add that a great store of useful information about the 

 diamond and the geology of diamond-fields in Australia, India, Brazil, and else- 

 where, has been brought together by the Eev. W. B. Clark, M.A., F.G.S., Vice- 

 President of the Eoyal Society of New South Wales, in liis Anniversarv Address 

 to that body on May^25, 1870 (8vo, Sydney, 1871).— T. E. J. 



