The “green rock,” or basaltic greenstone of the South Staffordshire coal-field, presents an interesting subject of geological research. The center of the formation, as also that of the eruptive agency of the tract, may be considered to be in the Rowley Hills, from which the latter diverges on all sides, setting off innumerable veins or vertical dykes, which are subdivided into smaller veins of a white color, and everywhere penetrating and altering the shales, sandstones, and coal metals. This igneous mass is more of an underground than super-surface rock, occupying an area of twenty-five square miles, and rising only into slightly-elevated and detached ridges. It corresponds, in mineral characters and position, with another extensive effusion of trap in the northern coal-fields, termed the “Whinsill.” This consists of a bed of basalt, which has been injected among the strata of the coal-measures, or, as some conjecture, has been poured over them as a cotemporaneous formation—an overflood of lava produced during the deposition of the mountain limestone group, and overlaid in turn by the succeeding series of upper strata. Nearly the entire coal-measures of the north of England have been more or less influenced by the eruption of the Whinsill, from which dykes are thrown off in every direction, accompanied by phenomena precisely similar to those exhibited in the coal districts of Scotland. In both countries the same agencies are thereby demonstrated to have been at work, originating in the same causes and producing similar effects, and doubtless cotemporaneous in their operations over these and other immense areas of the globe. The rocks which constitute the SECONDARY and TERTIARY DIVISIONS in the great geological series remain to be described. These, generally, all range eastward from the older formations, to which they succeed in the order of superposition. The line of section of the whole bears from Whitehaven on the north-west, to Newhaven on the German Ocean by south-east, where, along this course, every formation in the island is intersected, ascending from the granite of the Cumbrian mountains through all the intermediate series to the London clay and upper tertiaries. The strata of which these formations consist are all, more or less, inclined to the horizon, dipping under each other, and emerging in succession to the surface. The outcrop is at right angles to the line of section, so that each class of rocks rises to and faces the north-west, meeting the eye of the geologist as they are in turn approached, and narrowing in extent and receding in proportion as they are vertically removed from the older systems.