"(3) The microscopical structure and chemical composition of
the beds of cannel coal and earthy bitumen, and of the more
highly bituminous and carbonaeceous shale, show them to have
been of the nature of the fine vegetable mud which accumulates
in the ponds and shallow lakes of modern swamps. When such
fine vegetable sediment is mixed, as is often the case, with
clay, it becomes similar to the bituminous limestone and
calcareo-bituminous shales of the coal-measures. (4) A few of
the under-clays, which support beds of coal, are of the nature
of the vegetable mud above referred to; but the greater part
are argillo-arenaceous in composition, with little vegetable
matter, and bleached by the drainage from them of water
containing the products of vegetable decay. They are, in
short, loamy or clay soils, and must have been sufficiently
above water to admit of drainage. The absence of sulphurets,
and the occurrence of carbonate of iron in connection with
them, prove that, when they existed as soils, rain-water, and
not sea-water, percolated them. (5) The coal and the fossil
forests present many evidences of subaerial conditions. Most
of the erect and prostrate trees had become hollow shells of
bark before they were finally embedded, and their wood had
broken into cubical pieces of mineral charcoal. Land-snails
and galley-worms _Xylobius_ crept into them, and they became
dens, or traps, for reptiles. Large quantities of mineral
charcoal occur on the surface of all the large beds of
coal. None of these appearances could have been produced by
subaqueous action. (6) Though the roots of the _Sigillaria_
bear more resemblance to the rhizomes of certain aquatic
plants; yet, structurally, they are absolutely identical with
the roots of Cycads, which the stems also resemble. Further,
the _Sigillariae_ grew on the same soils which supported
Conifers, _Lepidodendra, Cordaites_, and Ferns--plants which
could not have grown in water. Again, with the exception
perhaps of some _Pinnulariae_ and _Asterophyllites_, there
is a remarkable absence from the coal measures of any form of
properly aquatic vegetation. (7) The occurrence of marine, or
brackish-water animals, in the roofs of coal-beds, or even
in the coal itself, affords no evidence of subaqueous
accumulation, since the same thing occu