Note 64 — Chapter XI

If it be correct to set down the North Greens coal-seam as really representing a terrestrial surface, that is, of course, a flat delta or plain scarcely raised above the sea-level, we must, I suspect, call in the aid of a slight elevatory process, or else hold that the depth of the sea at the locality where the lower limestone was forming did not exceed 80 or 90 feet, and may have been considerably less, and that this space came to be eventually filled up by the detritus of the river. But the wide extent and sometimes the great thickness of the limestone beds seem to indicate a greater depth, and thus favour the idea of an elevation of the sea-bottom to form the North Greens coal-seam.