Page:Quarterly Journal of the Geological Society of London, vol. 27.djvu/148

 laria*, Pecopteris†, &c. ; 7. Ferruginous sandstone, with a thick dendrites weathered out on its surface, from the same place ; 8. Sandstone, with fucoid (?) markings, from the same place.

§ B. From the Carboniferous Rocks of Lower Albany. — 1. Black shale (slickensided), with Stigmaria ; 2. Dark-grey granular quartz rock, with pyrites, from near the shale.

§ C. Crystalline Rocks. — 1. A variety of brownish steatite, fit for carving, from the Transvaal ; 2. Massive prehnite, from Bankberg, Cradock.

§ D. Crystalline Rocks from the Diamond-bearing Localities of the Orange and Vaal Valley.— 1. Block of calcite, from the Orange- river district ; 2. Specular iron-ore ; 3. Galena; 4. Block of crystallized quartz and galena ; 5. Lydite, with pyrites ; 6. Tremolite ; 7. Selenite ; 8. Amethyst, quartz, agate, and garnet, from the gravel.

Remarks. — With reference to A, No. 1, the direction of the prevalent currents of the Karoo formation might be learned from a study of these rippled surfaces. No. 2. Excavating the shales to examine if they would yield roofing-material, the author found these little bivalves [which are Estherioe, of a new species — T. R. J.]. They were found at one spot only. No. 3. These are water- worn, and furnish evidence, the author thinks, of great aqueous denudation. Their matrix is often, if not generally, permeated by igneous rock. [These and other specimens have the appearance of bones imbedded in volcanic ash. — T. R. J.]

Of the country formed of the Karoo strata Dr. Grey observes : — The sweet-grass country, Dutch " Zout- Veldt," yielding the valuable Karoo plant (Adenachoera parviflora) accompanies the Dicynodon- (Karoo) beds of the great plateau, beginning on the eastern side from about Queenstown, where the pasturage is of a mixed character, locally " Gebrokenveld." From that district it is traceable as in Bain's map, with its margin and watershed on the Zuurberg &c. The author is inclined to think that the bones of the Dicynodons were deposited in the shallow waters of an inland sea — the salts of soda that predominate largely in the salines of the soils of the great Karoo plains, and help to form the "back-grond" of of that region (sandy soil impregnated with common salt and carbonate of soda‡, and some salts of magnesia and alumina), supporting him, he thinks, in this view §.


 * [The cast of a portion of decorticated stem, in hard blue shale. — T. R. J.]

† [In a dark shale. Mr. Carruthers regards this Pecopteris as being probably P. Cistii (Brongniart). Alethopteris Lonchitidis, Stbg., and Asterophyllites equisetiformis, Brg. also accompany the foregoing. — T. R. J.]

‡ The ash of some native plant (" Ganna-bush ") growing on the plains is used extensively by the Boers in making hard soap, and contains a large percentage of carbonate of soda. The impure carbonate (lixivium), first mixed with sheep's tallow, is deprived of its carbonic acid by a long process of boiling, requiring two or three weeks to be properly effected.

§ [The presence of Estheria, which, as a genus, inhabits brackish water, is inimical to the idea of an open sea having formed the Cradock beds, though inland brackish lakes would not be inconsistent. A fragment of an Encrinite (in the Society's Museum) in one of the brecciated limestones of the Rhenosterberg