(1) Stratigraphical The exposed Carboniferous strata of the Leicestershire Coal-field are bounded on their western edge by a narrow strip of course current-bedded sandstones and conglomerates, which form the base of the Trias in this part of the country, and which are doubtless homotaxial with the typical Bunter Conglomerate of South Staffordshire, Shropshire, and Cheshire. These sandstones and conglomerates are about 120 feet in thickness on the extreme margin of the Coal-field, but when traced eastward for two or three miles, by the aid of several outliers, they are found to thin out rapidly, and, east of a line drawn north and south through Ingleby and Measham, are conformably overlapped by the Keuper. The Trias, throughout the greater part of the area, rests upon the truncated edges of Carboniferous rocks, either upon Coal-measures, or, in the northern part of the district, upon Millstone Grit or even Yoredale Shales; there are, however, found here and there, intercalated between the Bunter and the Carboniferous, some thin beds of purple marls, breccias, and sandstones, seldom exceeding in aggregate thickness 30 or 40 feet, but differing remarkably, in lithological characters, from both the overlying and underlying rocks. My attention was first seriously directed to these rocks during a re-survey, on the six-inch scale, of a tract of country lying immediately to the east of Burton-on-Trent, and the results obtained induced me to make a careful examination of the beds throughout the Coal-field; for, although described and mapped as Permian by the Survey geologists, doubts