Page:A Treatise on Geology, volume 1.djvu/205

 CHAP. VI. partly by the growth of cryptogamia, and the accumulations of leaves, branches, and fruits, the decay of local vegetation, partly by water-floated additions from not far distant surfaces. The land on which this accumulation was proceeding is then seen to subside in level, so as to be covered by river, estuary, or sea deposits, on which a new series of growths and water drifts accumulate a new bed of coal. In some cases the accumulation may be wholly from plants in sitû, in other cases, all the mass may have been water-drifted; often these causes have concurred or alternated. What is here sketched as the most probable general theory, is quite in harmony with the facts observable in connexion with the often buried forests of late Cainozoic and even historical age. Chat Moss, Waghen Fen, Thorn Moor, the Holderness lakes and river channels, yield plenty of cases so analogous that we cannot doubt of their illustrating the principles on which a large part of the ancient coal was accumulated. Inundations from the upraised land, littoral action of the sea, chemical decomposition of the oceanic waters, eruptive action of subterranean heat, vital action on the land and in the water,—these are the causes to which the formation of the whole carboniferous system is clearly traceable; and by comparing the effects of all these causes in that ancient period with what happen at this day, we shall find modern effects precisely comparable in kind, but altogether inferior in magnitude.

Where then was situated that ancient land, from which, according to our view, were swept the materials of the 1000 yards of sandstones and shales which inclose the coal deposits in most parts of England, and the continent of Europe? And recollecting that in the series of millstone grit and carboniferous limestone in the north of England occur other beds of coal, and several hundred yards in thickness of other sandstones and shales, again we ask from what land were the plants and earthy sediments drifted in such abundance over this limited area? In the discussion of this