Page:Quarterly Journal of the Geological Society of London, vol. 28.djvu/27

1871.] STOW VAAL-RIVER DIAMOND-GRAVELS. 7 kopjes is a dry river-bed, with a small pool (or " lagoon," as it is termed at the diamond-fields) near its centre. Along its southern bank are accumulations of exceedingly large boulders piled up upon rocks that have been scarped in many places by the action of the current. In very high floods a portion of the water still flows through this ancient channel ; and a number of trees, such as grow along the sides of the present course of the river, still fringe its margin.

Between this and the river itself is another great deposit of gravel (Cawood's Hope) rising about 30 feet above the level of the stream. It seems as if at one time it must have been continuous with the gravel mass on the northern side, now forming the Gong-Gong diggings. In that case, the river must have flowed along the ancient water-course alluded to, until it cut out for itself the new and more direct channel it now occupies. This Cawood's Hope accumulation of gravel is bound together by a reddish matrix, similar to that at Pniel. It is unstratified, and contains many interspersed boulders. An important fact connected with it, as well as with most of the diamantiferous gravels, is that in it are numerous worn fragments of fossil wood, very similar to that found in the forest-zones of the Karoo formation in the Stormberg and Draakensberg. A water-worn fragment of fossil bone has also been discovered, and fortunately preserved, I shall again allude to these interesting facts before closing the paper.

The depth of the gravel below the bed of the river here cannot be very great ; for immediately above this place there are some small rapids, caused by the rocks crossing the stream ; and near the middle a little island has been formed, principally of gravelly clay ; but no diamonds have been found in it.

Gong-Gong.— Abutting immediately on the northern bank of the river are the Gong-Gong diggings. These are spread over a deposit of gravel, extending along the banks of the river for a considerable distance. Its highest point rises some 50 feet above the level of the water. It is a very red gravel, intermixed with irregular patches of boulders ; all bound together with a clayey matrix, very similar to that of the Pniel Kopje. The gravel contains polished and worn specimens of various rocks. See "No. 1" in Appendix.

Section II. The Deposits at Klip Drift and Pniel*. — Pniel Kopje is nearly 150 feet above the river ; a large portion of it is composed of a vast accumulation of enormous boulders intermixed with an ochreous and very clayey matrix. The intercalated gravel is very similar to that found in the diamond-bearing deposits at Gong- Gong &c., the great difference being the preponderance of immense and thickly interspersed boulders of various kinds of rock. The pebbles it contains are shown by the specimens sent. See Nos. 3, 4, 5, 6, from Pniel, and Nos. 7, 8, 9, from Klip Drift, in the Appendix.

These were procured from one of the " cradles," without sorting,

'Mining Journal,' March 4, 1871, p. 190.— T. R. J.
 * For Mr. E. T. Cooper's map and description of this locality, see the