with black carbonized fragments of coal-measure plants, but without any of the shells and other marine organisms so abundant below. The topmost bed is a grey carbonaceous sandstone (16), underlying a thin covering of vegetable mould. [Illustration: Fig. 35.--Contemporaneous Trap.] Such is the skeleton, as it were, of the section; the mere dry bones which remain to the geologist, and which he must study closely to be able to give them life again. The lowest bed visible, with its stone-lilies and molluscs, we readily recognise as marking an old ocean-bed, so that the little episode in the primeval records of our planet here presented to us opens, like the two great epics of antiquity, within sound of the wide-roaring sea. The seam of ash which follows shows, from the sharpness of its line of demarcation with the limestone, how the denizens of the sea-bottom were suddenly destroyed by a thick shower of volcanic dust that settled down over their remains. The waters, however, soon cleared, and ere long stone-lilies and producti were plentiful as ever, mingling their remains among the upper layers of the soft muddy ash, and giving rise therefrom to a sort of calcareous ash or ashy limestone, until in the course of time the volcanic matter became wholly covered over by a seam of ordinary limestone. The corals and stone-lilies were, however, anew destroyed by the deposition of volcanic dust that settled over them as a seam of ash, after which the water was again rendered turbid and muddy by the inroad of foreign matter, which, brought down by rivers or by the changing currents of the ocean, sank to the bottom and eventually consolidated into a seam of shale. Thereafter the volcanic forces began once more to eject a quantity of dust and scoriæ that fell into the water and spread along the bottom as a stratum of ash, and to pour out a current of lava which hardened into a great sheet visible now as the undermost greenstone of the section. The emission of the lava seems to have terminated the eruption, for the next stratum is one of shale like that below the ash, so that the muddy sediment, the deposition of which was interrupted for a while by the volcanic products, began afresh to settle down along the sea-bottom. This last condition of things seems to have continued for a considerable period, seeing that the shale bed is relatively thick, and from its fissile laminated structure indicates a slow and tranquil deposition. Another eruption of volcanic dust and ashes again interrupted the detrital deposits, and gave rise to another seam of tufa. This last subterranean movement seems to have considerably altered the general contour of the sea-bottom, and so elevated it, at least at one part, that a thick accumulation of sand, and subsequently of clay, filled it up to the level of the water or nearly so, giving rise to a dense growth of the stigmaria and other coal-measure plants whose roots are