On Insoluble Residues obtained from the Carboniferous-Limestone Series at Clifton

Abstract

The Carboniferous-Limestone rocks at Clifton are well known and have been the subject of several communications to the Geological and other Societies. Among the authors of such communications I may mention Sir H. de la Beche, Sir A. Ramsay, Dr. Buck]and, Mr. Conybeare, Mr. Etheridge, Mr. Tawney, and Mr. Stoddart; the papers and monographs written by the investigators just named deal mostly with the physical, stratigraphical, or palæontological problems which the rocks of the gorge of the Avon have presented for solution; I am not aware that any one has examined the residues obtained from the limestone after boiling portions in strong acid. Professor Hull's classification of the Carboniferous series seems to me to be the most comprehensive yet produced; but there may be some difference of opinion as to the term Yoredale when applied to the Upper Limestone of the Bristol and Somersetshire coal-fields. If Professor Hull means, by the term Yoredale, the beds which mark those physical conditions which closed the Limestone Period and ushered in the Millstone Grit and Coal-measures, then he is correct in saying that there is at Clifton a series of deposits, represented by a thickness of about 100 feet, which mark the close of the Limestone Period and the coming in of the Millstone Grit. They are the beds referred to by Sir H. de la Beche as “Upper Mixture of Sandstones, Marls, and Limestones.” Hitherto the limestones known as the “Black Rock” have been regarded as the base of the Middle