of clunch or clay rising for sometimes at least 8 feet above the floor of the coal around them. If they were accumulated under water, but the surrounding coal that abuts against their base was begun to be formed at or above the level of the water, we must necessarily suppose an elevation of the ground to have taken place to the amount of 8 feet, between the time of the formation of the "swells," and that of the coal, or else that they were formed during seasons of flood when the waters were 8 feet higher than usual. The structure of these "swells" seems to me a very small foundation on which to build the hypothesis either of a partial eight-foot elevation of the land, or for an eight-foot rise of the water. If, however, both "swell" and coal were formed under water, there is no difficulty in the case.
2nd. The rock faults in the Thick coal.—These were described pp. 45 to 51. Figs. 5 to 8. The most obvious questions to put respecting them, when we are inquiring into the origin of coal, are, if the sandstone was deposited in water, and the coal is so intimately and minutely interstratified with the sandstone, how comes it that the coal was not itself deposited in water? or, if the coal is of terrestrial origin, must not the sandstone be so too? The only possible origin[1] for the sandstone I can imagine on the latter alternative is, that the sand was brought up in among the vegetable matter by means of a strong spring or springs, but whether such an imagination be allowable to account for a mass of sandstone of 250 by 400 yards in extent, at least, must be left to the decision of the reader. There is, perhaps, at first a little difficulty in understanding this local accumulation of sand over a comparatively small area, surrounded by so much almost unmixed coal, even on the supposition of their both being drifted into the place we now find them, and deposited under some considerable depth of water, but in this case it is nothing more than the local occurrence of a cake of sandstone among wide spread beds of clay, or other material, a case which we know frequently occurs in nature.
More recent examination of the sand patches in the Thick coal of the Causeway Green colliery, and accounts of similar occurrences in many other parts of the neighbourhood, and the ending of the Thick coal in beds of sandstone in various directions, have only confirmed me in my belief in the entirely subaqueous deposition of those coals.
The way in which thick and thin seams of sandstone and coal alternated occasionally, with little seams of perfectly bright pure coal in the regularly stratified sandstone, while thick beds of pure bright coal are often flaked by little partings of clean sand throughout their thickness over considerable areas, seems to me to render it impossible to suppose otherwise than that their deposition and stratification was produced by the same agent.
It seems to me absolutely necessary to suppose that the vegetable matter was strewed out in regular thin laminæ at the bottom of
- ↑ It is clearly impossible it can have been "blown" sand.
