In that case we could not too
readily imagine the forest-clad region sinking below the waves,
being buried under the deposits of the rivers, and then emerging,
thousands of years later, to receive once more the thick mantle
of sombre vegetation. Probably there was less rising and falling
of the crust than earlier geologists imagined. But, as one of the
most recent and most critical authorities, Professor Chamberlin,
observes, the comparative purity of the coal, the fairly uniform
thickness of the seams, the bed of clay representing soil at
their base, the frequency with which the stumps are still found
growing upright (as in the remarkable exposed Coal-forest surface
in Glasgow, at the present ground-level),* the perfectly
preserved fronds and the general mixture of flora, make it highly
probable that the coal-seam generally marks the actual site of a
Coal-forest, and there were considerable vicissitudes in the
distribution of land and water. Great areas of land repeatedly
passed beneath the waters, instead of a re-elevation of the land,
however, we may suppose that the shallow water was gradually
filled with silt and debris from the land, and a fresh forest
grew over it.
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