Page:Transactions of the Geological Society, 1st series, vol. 3.djvu/257

 and of all sizes, from a hazel nut to an ordinary potatoe. The shape of the bed also deserves notice; its general thickness is about fifteen inches, which it preserves for near thirty yards, as appears in the section of the quarry; it then diminishes at each end to a thin edge, and at length totally disappears. At a short distance in front, there happens to be left by the quarry-men an insulated butt, where this bed is not found at the level where it might be expected; the conclusion therefore is, that it has terminated also in this direction in a similar manner: thus, as to its figure, putting the practical geologist in mind of the mineral deposit called a pipework in the lead countries. I must however observe that in an extensive pit at Kneesworth on the other side of the county, the same bed occurs again, where it preserves an uniform thickness and direction like the other beds with which it is associated. In general, I take this to be the bed which Mr. Townsend notices as hard and rubbly, and found in descending the hills from Everly to the vale of Pewsey. It has also been observed by Mr. Warburton at Marlborough.

I have never been able to observe any strong line of separation betwixt the clunch and the succeeding stratum of gault on which it rests. I believe they pass by degrees into each other. The lower beds of clunch become more sandy, and gradually assume the nature of an argillaceous loam. In the next observable stage of transition, the mass assumes a greenish grey colour, and a plentiful admixture of dark green sand is uniformly dispersed through its substance. At the same time it contains numerous irregular dark brown nodules of a ferruginous indurated marl. At length these foreign matters disappear, the mass becomes uniform and ends in the bluish clay or argillaceous marle called