Few students of Geology can doubt that the elevation of the Weald has been the most important factor concerned in determining the present surface-geology of the south-east of England. It has been constantly before my own mind in all my studies of Tertiary Geology for the last ten years, as the problem to the solution of which many other preliminary questions required answers. In my first paper on Tertiary Geology, read before the Geologists' Association in 1883, I pointed out that the presence of Eocene pebble-beds in the Woolwich and Reading series and in the Bagshot series afforded strong evidence of the encroachment of the sea upon the Upper Chalk in Eocene times. This conclusion is accepted by our greatest authority on Tertiary Geology, Prof. Prestwicb. The fact alone furnishes a strong presumption that the elevation of the Weald had commenced before the close of the Eocene period; while the many outliers of the Woolwich and Reading beds at high altitudes on the N. Downs, taken along with the general absence of the London Clay there, seems to tell us that the initial elevation of the Weald hill-range had gone far enough for this to form a shore to the area of deposition of the London Clay. I have shown further, in a former volume of the Geol. Mag., that, though there is no absolute proof, there are grounds for believing, that certain outliers of sands on the N. Downs (at Chipstead, Headley, and north of Netley Heath) are more likely to turn out to be of Upper Eocene age, than of any age to which they had been hitherto assigned by different writers.

I Have elsewhere pointed out the importance of the two factors —(1) the lateral force which produces the metataxic work (quâ cleavage), (2) the resistance offered to the movement of the constituent particles of a rock-mass in the direction of cleavage-dip (in some cases) by the dead weight of the superincumbent mass; the relative value of the two modifying (in the case of a deep-seated rock-mass) the whole metataxic result. Mr. Harker applies the idea in some criticisms of a paper of General MacMahon's on the “Crumpled Culm-measures of Bude ” (See Geol. Mag. April, 1890).

Amongst the specimens sent many years ago, from South Africa, by the late Mr. Andrew Geddes Bain, to the Geological Society of London, are two small blocks of greenish-grey hard mudstone or shale, very slightly calcareons; one bed-plane in each, specimen bears upon its surface numerous valves of one or more forms of small Lamellibranchs, closely resembling the shells of the genera Cyrena and Cyclas in contour.

In the deposits previously described what takes place appears to be about as follows. The larger flakes of biotite undergo an alteration which largely produces epidote, and not improbably granular rutile, though this is not at all proved. Crystals of rutile very rarely result during the process. Such of the iron of the biotite as is not combined in the epidote (which is strongly coloured) is removed in solution, some of it being deposited again as limonite diffused throughout the deposit, and some taking part in the formation of the thin bands of ironstone, being precipitated as carbonate.

In the Geol. Mag. for July, 1875, p. 326, the writer of the present note gave some data bearing upon the rate of weathering of certain limestones of the Lower Carboniferous Series, deduced from the observed extent of waste that had affected some dated tombstones in Kirkby Stephen Churchyard. The series of observations of which that formed a part were suggested several years previously by the fact that many of the rough blocks of limestone used for walling in that neighbourhood had evidently suffered considerable waste since the erection of the walls, and this especially on the upper and outer surfaces of the stones referred to. In a few of these cases (as well as in many other cases observed since) it was perfectly evident that, since the coping stones had been placed in their present positions, the waste of the limestone by atmospheric causes had proceeded to at least as much as a quarter of an inch. This was evident from the fact that thin, delicate, fragments of Corals, Brachiopods, Encrinites, etc., were left standing out in sharp relief to that extent above the general surface of the adjoining limestone matrix.

There is some doubt as to this being the type. The specimen in the Bristol Museum so referred is stated to have come from “Warminster,” but Sowerby gives “Blackdown” as the locality of his type. The specimen in this Museum agrees very well with Sowerby's figure, and also with Davidson's reproduction of the same (fig. 31, supra), but not with fig. 32, the specimen stated by him to be in the Bristol Museum.