CHAPTER III. MAGNESIAN LIMESTONE OF THE PERMIAN FORMATION. This formation ranges in a nearly north and south direction through the North-east of England, from Tynemouth to Nottingham ; disappearing, however, beneath the New Red Sandstone for a few miles in the neighbourhood of North Allerton; and generally forming the escarpment of an elevated plateau, over looking towards the west the coal-fields of Durham, Yorkshire, Derbyshire, and Notts. The formation is interposed between the Carboniferous rocks below, and the Triassic rocks above, and is unconformable to both. Hence the Permian strata may he found resting in some parts on upper beds of the Coal-series ; in others, on lower beds of the Millstone Grit; while, on the other hand, the New Red Sandstone rests on dif ferent members of the Permian series, or (as already observed) passes over and rests directly on Carboni ferous strata. The Magnesian Limestone series of Durham has a thickness of about 300 feet, and is overlaid by red marls with gypsum ; it reposes in turn upon marl slate, and Lower Permian Sandstone, the whole series