West side. East side. Thin Magnesian Limestones and Marls Magnesian Limestone Hilton Shales Marl Slate Penrith Sandstone and Brockrams Lower Permian Sandstones. _Description of the Strata._ On the east side of the Pennine Chain, the Lower Permian sandstone is an inconstant deposit often consisting of yellow false-bedded arenaceous strata. The Marl Slate is an argillaceous shale, often containing bituminous matter, and yielding several fish-remains and some plants; it is usually only a few feet in thickness. The Magnesian Limestone is typically developed in Durham as a yellow or greyish limestone containing a variable percentage of carbonate of magnesia; when traced southward, it alters its characters, becoming mixed with mechanical deposits, and some chemical precipitates in places, so that at Mansfield it appears as a red sandstone with grains cemented by a mixture of carbonates of lime and magnesia; and, like the rest of the Permian strata, it has disappeared when we reach Nottingham. In addition to the southward thinning of the Permian beds of this area, there is some evidence of their disappearance in a westerly direction, though, as the present strike of the beds is nearly north and south, the indications of this are less convincing. On the east side of the Pennine Chain, the main difference observable is the relative thickness of the major divisions. The Lower Permian sandstones have thickened out considerably, while the reputed representatives of the Magnesian Limestone are thin. The Penrith sandstone is of considerable interest. It contains in places, as near Appleby, thick deposits of breccia consisting of angular fragments chiefly composed of Carboniferous Limestone, which in many cases have undergone subsequent dolomitisation, embedded in a matrix of red sandstone. This breccia is known as brockram. Many beds of the Penrith sandstone are composed of crystalline grains of sand, due to deposition of silica in crystalline continuity with the quartz of the original grain after the formation of the deposit; of more significance, for our present purpose, is the presence of other accumulations of the sand, in which the individual grains often approach the form of spheres, thus resembling the 'millet-seed' sands of modern desert regions. The Hilton shales are grey sandy shales, with plant remains, and above them are variable deposits including thin magnesian limestones which have yielded no fossils. The isolated Permian deposits of the midland and southern counties of England consist of red marls and sandstones with occasional breccias, and in the absence of fossils, their exact position in the Permian series is still unknown.