prostrate stems and matted thickets of ferns, that sank slowly down beneath a deepening sheet of sand and mud. Often, too, the sea must have flooded, perhaps for years, the flat delta-lands, carrying with it its own productions, such as the lingulæ and cardiniæ, which we find among the coal seams. And thus the process went on during the long ages of the Carboniferous system. Forest after forest spread its continuous mantle of green athwart the low swampy lands of that old delta, and each in succession foundered amid the muddy waters, now of the ocean and now of the river, that strewed over its site a rich detritus which went to form the soil of new jungles and forests. The Edge series measures from 800 to 900 feet in depth, so that the depression must have been carried on till the forest that once grew nearly on the sea-level had sunk 800 feet below it This process was undoubtedly a very slow and tranquil one. Yet geologists used to regard these frequent changes of sedimentary matter as so many proofs of repeated catastrophic submergences, when the ocean came rolling over the land, prostrating forests, uprooting the hugest trees, and leaving the scattered bones and scales of fishes amid vast accumulations of mud and sand, where but lately there had bloomed a luxuriant vegetation. But the sober and diligent student of geologic fact will read in these rocks no such record of cataclysms. He will see in them evidences of the same gradual and sure operation which marks the processes of Nature at the present day. He will note how during a tranquil and probably imperceptible submergence of the river-bottom, forest after forest sprang up, flourished perhaps for ages, and eventually settled down beneath the waters of the river and sometimes of the ocean, amid ever increasing accumulations of mud and sand. Musing on these ancient changes he will be lost in wonder at the immense duration of the period during which they were in progress; and he will try in some measure to realize the features of their scenery. He will picture the delta with its ever-varying islets and sand-banks, its lakes and submerged forests, its leafless trunks peering above the water and sticking along the shoaling mud, and its crowded jungles that cover every drier spot. He will cast his eyes to where the delta opens out into the ocean, and mark how the waves encroach upon the mud-banks, cutting away what the river has piled up, and washing the roots of gigantic trees that wave their green coronal of fronds above, and overshadow the rippling of the green sea below. He will try to thread the windings of the stately river through brakes of ferns and calamites, and banks richly hung with tree-ferns and sigillariæ, and then upward through dark shaggy pine-woods, silent and gloomy, with the water creeping lazily through the shade or dashing in white cascades over dripping rocks, and onward still, far away among the distant hills till the fountainhead of the