OF SOUTH CAROLINA. 47 
to suppose that they could have been removed from the spot where they grew, without having their 
forms entirely destroyed. 
That the greater portion of the coal plants lived and died where we find them, there can be no 
doubt. Many of our swamps present such a state of things as may be supposed to have existed 
in those ancient coal-fields while their plants were yet growing. We have a depth of vegetable 
matter, often amounting to 20 or 30 feet, composed of the trunks of fallen trees, roots, and leaves, 
in all stages of decay; and upon this a dense growth of ferns, reeds, vines, and other luxuriant 
plants that love shade and moisture. ‘These swamps are sometimes partially submerged by the 
muddy water of our rivers during freshets; a deposit of mud is often left, which is quite sufficient 
to show us how the most delicate plants may be enclosed, and their impressions preserved with 
great accuracy. If a subsidence of the whole be now supposed to take place, so as to allow of its 
being overflowed by the waters of the sea, it would, in time, be covered by sedimentary matter, 
which would enclose marine shells and fishes, such as we find in the sandstones of the coal 
measures. Heat applied below, under these circumstances, would char the vegetable matter and 
convert it into coal. 
So far this hypothesis is plain ; and very rationally accounts for the formation of one bed of coal, 
but where there are several beds, one above the other, we are obliged to suppose the elevation of the 
submerged coal-field sufficiently above the water to allow of another and a similar accumulation of 
vegetable matter: subsidence must again take place, and this matter be converted into coal. This 
alternate subsidence and elevation must be repeated for every seam of coal present in a coal-field. 
The difficulty is to account for this repeated, and often apparently regular oscillation of the earth’s 
surface. 
The basin shaped depressions in which coal is found, is remarkable, but is far from being 
universal, and is probably accidental, and not necessarily connected with the formation of coal. 
The long trough-like coal-fields of Alabama are the result of the elevatory forces that upturned the 
edges of the underlying Silurian rocks. 
The Flora of the Carboniferous System is characteristic of a damp, warm climate, such as at 
present is peculiar to the islands within the tropies, for the luxuriant tree ferns of the coal formation 
have no representatives elsewhere. 
Speculations upon the causes that have reduced such a climate to that of the present period, 
would lead us beyond the limits of a mere outline. Mr. Lyell,* who has treated this subject with 
his usual distinguished ability, attributes these changes of climate to an alteration in the relative 
distribution of land and water. ‘The milder climate of insular, compared with main land, in the 
same latitude, is well known; and there can be no doubt that groups of islands such as marked 
the carboniferous period, would have the temperature of their atmosphere, and consequently their 
climate, greatly altered by being converted into continents. But it may be doubted that such a 
cause is alone sufficient to account for the extent of the changes of temperature that have taken 
place in past periods. 
As may be inferred from what has been already said, the characteristic feature of the organic 
remains of this system, consist in the vast number of fossil plants, which amounts to one half of 
all the known species. ‘“ 
* Principles of Geology. 
* 
