some granite, and with the apparent silicification of some bands of schist, covered unconformably by sandstone, through which water had carried silica to replace the original felspar and mica of the gneissic bands below. This view of the metamorphic condition of some quartzites Dr. Rubidge regarded as a key to the elucidation of certain sections seen in different parts of South Africa, and considered by him to be of a very difficult nature, if left to be explained according to the usual view of geologists. Thus, in 1858 (Geol. Soc. Journ. vol. xv. p. 196), he explained the section of Mitchell's Pass, at the village of Ceres, otherwise than Mr. Bain had interpreted it; and regarded the great sandstone formation of Table Mountain as occurring again and again, in great patches of horizontal and unconformable beds, over the highly inclined schists and gneiss, both of the Cape and of Namaqualand, instead of dipping at Ceres down below the Devonian rocks of the Bokkeveld; and thus he made the schistose rocks of Cape Town, of the Bokkeveld, George, and southern Uitenhage (whence he got Devonian fossils) to be all of the same date. Certainly a great advance was made in proving the continuation of the Bokkeveld schists into the last-named district; but whether the schists and slates of the Cape come into the same category still requires careful inquiry.
Examining the neighbourhood of the Zuerberg, in occasional journeys, Dr. Rubidge endeavoured to throw light on the stratification and structure of that country, showing that the Lower Ecca beds are probably of Devonian age. For the illustration of his views on this matter, he sent several series of rocks and fossils to the Geological Society of London, and he communicated papers on the subject to that Society, to the 'Geologist,' to the British Associon, and to the periodicals of Port Elizabeth. In 1864 he visited England, and travelled to the north with the special view of studying schistose and quartzose rocks like those of the Zuerberg. He brought with him many new fossils, of Secondary age, from the Uitenhage district, and went to considerable expense in getting them properly examined and determined, intending ultimately to produce a general work on the geology of the colony. The fossils constituted a valuable addition to the South-African collection in the Geological Society's Museum, and were fully described, with illustrations, in the Society's Journal, by Mr. E.. Tate, in 1867.
So long ago as 1854, Dr. Eubidge wrote to his geological correspondents in London on the subject of aerial denudation, which had not then received so much attention from European geologists as it deserved. In 1866 he reproduced the chief points of his letters in the 'Geological Magazine,' No. 20, bringing forward evidence of the enormously extensive and long-continued denudation of the interior of South Africa, subsequent to its leaving the sea and since the lacustrine deposits of the Karoo formations were drained dry.
As an observer and as a generalizer, then, Dr. Rubidge was energetic and bold, adding much to the store of geological facts and thought, though working hard throughout in his professional prac-
