6 PJaOCEBDIJSTGS OP THE GEOLOGICAL SOCIETY. [I^OV. 8, 



spersed throughout, bound together with a calcareous cement ; as is 

 the case at Hebron and Diamondia (figs. 1 & 2, c). 



These gravels, wherever found, contain large quantities of small 

 fragments of fossil wood. 



3rd. Irregularly stratifiedgravelly clays of various colours. Some 

 of these also contain irregular patches of boulders. Examples of 

 these are met with at Hebron and Diamondia (fig. 2). 



4th. A pebbly drift, without large bonlders, and bound together 

 by a red ferruginous and rather clayey matrix. This is the case at 

 Jager's Fontein. 



5th. A gravelly sand of difi'erent shades of colour; the upper 

 generally white, with irregularly interspersed boulders. This de- 

 posit is rather contorted in some places, and is found at a much 

 lower level than the others. 



Section I. 1 have not been able to procure many sections. One 

 of them (fig. 1) comprises Natal Kopje, Cawood's Hope, and Gong- 

 Gong ; from all of which places many diamonds have been procured. 



Natal Kopje. — On the summit of Natal Kopje there is a dark blue 

 gravelly clay, with boulders (1) ; below this is a yellowish clay, inter- 

 mixed with calcareous tufa (2) ; and beneath this is a reddish, 

 oehreous, gravelly clay (3). These clays are very irregular in thick- 

 ness, altering very much in a short distance ; their total thickness 

 varies from 2 to 4 feet. The largest diamonds (up to the present 

 date, July 1871) have been here found within a couple of feet of the 

 surface. 



Below these beds is a great deposit of gravel {d). Its true thickness 

 has not been ascertained ; but shafts have been sunk into it for up- 

 wards of 30 feet without reaching the bottom ; it is probably much 

 thicker. It contains multitudes of pebbles of the various rocks found 

 in the diamond-deposits. The peeuhar shape, rather flat and oval, 

 which many of them have, has caused the diggers to name them 

 " kidney-stones ; " they are thickly packed together in some portions 

 of the gravel. 



Upon what rocks this deposit rests is not known ; but connected 

 immediately mth it is a subterranean escarpment of a rock («) called 

 by the diggers " rotten-stone " (" decomposed felspathic trap," 

 Jones*), which they describe as a kind of " cone-within-cone," 

 decomposed, rotten sandstone, breaking up in concentric layers, with 

 hard, firm nuclei, resembling boulders. A shaft has been sunk down 

 the face of this underground precipice for upwards of 30 feet, as 

 shown in the section (fig. 1). Dense patches of such large pebbles as 

 are found in the gravel seem to be massed along its front. This 

 rock slopes ofi" towards the land side, and is there covered with gravel 

 (e), and boulders are spread over the surface. This gravel is about 2 

 feet thick ; as yet no diamonds have been found in it. 

 - Cau'oocVs Hope. — Joining the Natal Kopje at rather a lower level, 

 are two smaller kopjes, composed of a deposit similar to that found 

 iu the Natal Kopje. At the foot of a small ravine leading from these 



* " Notes on specimens from Klip Drift and Pniel, by Prof. E-upert Jones," 

 Mining Journal, March -i, 187J, p. 190.— T. E. J. 



