Page:Quarterly Journal of the Geological Society of London, vol. 27.djvu/698

 central point at the top (see map, fig. 10). There is no displacement or alteration in the composition of the strata where they come into contact with the dykes. Dr. Rubidge thought that such dykes were formed by cracks due to the shrinking of the strata, and filled up in the same manner as deposits are supposed to take place in some mineral veins.

The combined thickness of strata in the two sections (figs. 8 and 9) amounts to about 1200 feet for this portion of the Dicynodon or Karoo formation ; but this is evidently but a very small part of their entire thickness ; for, taking the dip from the Zwart Kei to the Stormberg, at angles varying from 4 to 7 degrees towards the N.W., and on the Dordrecht side of these mountains, dipping at the same angles towards the S.E., it is highly probable that the central thickness of this portion must be enormous. Very little will be known of their true history until the sections of every intervening mountain-side are fully described. Some time, however, must elapse before this can be accomplished, as many parts of the country are still occupied by the native tribes.

Dr. Livingstone's discoveries seem to throw some light on the origin of this formation, viz. an elevated plateau, with successive chains of lakes and marshes, that have been silted up, and subsequently the basins we find in the present day denuded out of the strata thus formed.

Accompanying the fossils mentioned in this paper, I have sent a packet given to me by Mr. C. W. J. Powell, and collected by him near the Upper Zwart Kei*. The large skull, so remarkable for its peculiar rows of small teeth (D. S. 41 . Probably Labyrinthodont. — T. R. J.), was also found in the same neighbourhood by Mr. Powell ; but I am not able to point out the exact strata from which any of these were obtained. I have also enclosed casts of stems from Kneehalter's Neck, given tome by Mr. John M'Donald†.

Section of the Stormberg on the Klaas- Smit's River. — After finishing my account of the Dordrecht and Zwart Kei sections, I obtained much valuable information with regard to a section of part of the south face of the Stormberg from Mr. Charles Evans‡, who has explored a large portion of the range in search of coal.

This section (fig. 11) illustrates some of the strata between the other two, near the synclinal axis of what I will term " the great Stormberg basin "§.

obscure surface-marks. 3. Very fine-grained sandstone, bearing mud-ripples. 4. Sandstone, with cast of Calamites or Equisetites ? 5 and 6. Obscure casts. — T. R. J.
 * No. 1. Rippled, fine-grained sandstone. 2. Ferruginous sandstone, with

† Nos. 7, 8, and 9. Sandstone casts of small portions of striated stems (Equisetites or Calamites ?). — T. R. J.

‡ For some notes by Mr. Evans of Queenstown, on the Coal of the Stormberg, see the ' Mining Journal' Jan. 14, 1871. — T. R. J.

§ It is worthy of remark that, as in other instances more numerous than they were once thought to be, the Stormberg range is a synclinal mountain ; for, as has been shown at Dordrecht, Buffel Doorns Flat, &c, the strata of the north and south dip towards and into it.