been laid down under circumstances inimical to animal and vegetable life; and these circumstances, judging from similar deposits in other countries, have been brought about by the action of ice.
5th. That such gravels as those marked E, F, and G, in Section, fig. 2, were probably rearranged from more ancient gravels in a trough eroded in the rocks forming the floor of the Vaal valley.
In compiling this paper I have been greatly indebted for notes and descriptions to Messrs. Shepstone, Donald, White, Kedger Tucker, Cronin, Key, Scott, Ella, Southey, Graham, Whitmore, and several other gentlemen.
Postscript, July 6, 1871. — Since writing the above, I have been informed by Mr. Tobin, who has travelled along the valley of the Vaal from the Draakensberg to Pniel, that he has traced agates along its entire course, and that at Harrismith, twenty-three miles on the Free-State side of the mountains, a very extensive zone of fossil wood makes its appearance. Mr. Tobin also showed me some sketches of the road over the Draakensberg, which reminded me forcibly of the peculiar rounded (glaciated) contours that I described in my former paper as noticeable in the Katberg*.
Lastly, Mr. George Gilfillan, who is at present on a visit to Queenstown, tells me that a short time ago he discovered near Pniel a large boulder with strice distinctly marked upon it, and that since then he found at " Moonlight Rush " that almost every boulder in the gravels there has most unmistakable markings of the same kind upon one or more sides. This appears to me a most satisfactory and important discovery with regard to the deposits we have been considering, and one which must definitely settle the question as to the conditions under which many of them were laid down. G. W. S.
Appendix. — Description of Specimens sent by Mr. Stow. By Prof. T. Rupert Jones, F.G.S.
In a letter, dated October 10, 1871, Mr. G. W. Stow states that, after a three week's visit to the Vaal-River Diamond-fields, he feels certain the description given of the diamond-gravels in the foregoing paper is correct, and that no other agency than that advocated in it could have formed the accumulation of boulder- drift, the river- deposits being distinct.
In determining the nature of these specimens, Thomas Davies, Esq., F.G.S., of the British Museum, has kindly given me his assistance.
No. 1. From Gong-gong. See page 7.
Washed, coarse, agate gravel†, containing : —
Veined Jasper, one pebble.
Yellow and white Quartz, several pebbles.
- See Quart. Journ. Geol. Soc. vol. xxvii. p. 539.
† A small dressed (?) fragment of rock-crystal was sent with this parcel.
VOL. XXVIII. PART I. C
