Page:Quarterly Journal of the Geological Society of London, vol. 29.djvu/480

 communication. A subsequent portion of the journey up the Hart, across to the Vaal, down the valley by the diamond-diggings of Hebron and Klipdrift to the Panneveldt, will be treated of in another paper.

From the Modder, first south-westward and then westward, to the junction of the Vaal and Orange, the olive shales of the Dicynodonor Karoo- series, traversed frequently by igneous rocks, form the country, and are seen in some places to lie unconformably on older rocks. The shales reach to the edge of the Campbell Randt. on the other side of the Orange River, and have been, it seems, to a great extent, formed of the debris of those old hills. The oldest rocks of the locality are seen cropping out here and there in the gorges at the foot of the Randt, and consist of metamorphic rocks, greatly denuded, on which the massive and extensive siliceo-calcareous strata of the Great Campbell Plateau lie unconformably. These latter and the breccias of their slopes are coated thickly with enormous travertine deposits. Beyond the Plateau, at Griquatown, a long parallel range of jaspideous rocks comes out from beneath the Campbell Plateau, presenting a wonderful group of yellow, brown, chocolate, and red jaspers, with magnetic and other ironstone, and beautiful seams of blue and yellow crocidolite. The southern portion of this range has long been known as the " Asbestos Mountains " and the " Doornberg." Igneous rock-masses occur around Ongeluk, west of the Jasper range ; and then bright-red jasper rocks crop up near Matsap, succeeded to the west by the parallel quartzite range of Matsap, and again by other bedded jaspers, which seem to be in a synclinal of the quartzite rocks, which come up again in the Langeberg. These are succeeded by lower rocks, consisting largely of sandstone, grit, and quartzite, with more or less pervading mica, as far as the journey extended in the Schurwe Bergen, also parallel to the former ranges. The maximum thickness of the successive strata is calculated by the author at 24,000 feet; allowing for possible reduplications, the minimum is regarded as not less than 9000 feet. The details of stratification, successive upheavals, denudation, nature and origin of the salt-pans, escarpments, river-valleys, and other features were treated of by the author, who has supplied a very large collection of specimens illustrative of the phenomena observed in the line of march, and of his numerous sections, maps, and sketches.

Discussion.

Prof. Hull suggested making thin slices from the limestone with a view to microscopic examination, and offered to carry out this suggestion.

Prof. Hughes observed that, by burning a limestone and suddenly plunging it in water, fossils previously invisible were sometimes manifested.

Prof. Rupert Jones pointed out some interesting lithological characters in some of the micaceous, jaspideous, and other rocks sent by Mr. Stow.