Page:Quarterly Journal of the Geological Society of London, vol. 33.djvu/45

Rh the Permian strata; this limestone is traceable over a large portion of that coal-field. From Mr. Howell's description, I imagine that the sandstones and breccias of group 2 are not much represented in the district, and that the calcareous conglomerates interstratified between purple sandstones and red marls belong mostly to group 3 of my sections. The sandstones and marls of group 4 were proved in a boring near the town of Warwick; but detailed sections of this group are much needed.

Section 16 represents the magnesian conglomerate of Somersetshire. I have felt considerable hesitation in including this section among Permian strata, because of the degree of uncertainty which seems to prevail as to its true stratigraphical position. Mr. Etheridge, in his able memoir on the subject, reasoning chiefly from fossil evidence, places it towards the base of the Keuper sandstone. In the sections of the Geological Survey, its true position is left somewhat an open question. Local geologists also appear undecided on the matter. Prof. Sedgwick, in 1832, spoke of its resemblance to the Alberbury conglomerate, and placed it on the same horizon as that deposit.

In 1854 Sir R. I. Murchison described this conglomerate as having "usually been placed on the same parallel as the Magnesian Limestone of the north of England; and the analogy of the succession in Shropshire, where the Lower Red Sandstone is interpolated between the coal-fields beneath and the magnesian conglomerate, favours the view." Prof. Phillips described these lower beds as "red or claret-coloured sandstones and marls, chiefly the former." Probably this diversity of opinion is owing in part to the fact alluded to by Prof. Ramsay as shown by Sir Henry De la Beche, that the conglomerates of the district are of various ages; so that the different authors may be speaking of conglomerates of ages widely apart. Personally I only know the conglomerates of the country between Wells and Shepton Mallet; and on reviewing the whole question, I am inclined, from the great similarity in colour and composition, as well as from the apparently greater similarity of the underlying sandstones and marls to those of Permian than to those of Triassic age, to regard the conglomerates generally as belonging to the former period rather than the latter. The inferences drawn in this paper, however, are not affected by this question; and the section need not be taken into account by those who differ from my opinion of the age of these conglomerates.

Section 17 is the original typical English section, as given by Prof. Sedgwick in 1832. And really, when I look at the completeness of that section, exhibiting, as it does, all the groups in almost every known variety of strata, and read the lucid and comprehensive memoir in which they are described, I wonder that English geologists were