This mass of
coal I saw quarried in the open air at Mauch Chunk, on the Bear Mountain. The
origin of such a vast thickness of vegetable remains, so unmixed, on the whole,
with earthy ingredients, can be accounted for in no other way than by the
growth, during thousands of years, of trees and ferns in the manner of peat-- a
theory which the presence of the Stigmaria in situ under each of the seven
layers of anthracite fully bears out. The rival hypothesis, of the drifting of
plants into a sea or estuary, leaves the non-intermixture of sediment, or of
clay, sand, and pebbles, with the pure coal wholly unexplained.
(FIGURE 430. Uniting of distinct coal-seams.)
The late Mr. Bowman was the first who gave a satisfactory explanation of the
manner in which distinct coal-seams, after maintaining their independence for
miles, may at length unite, and then persist throughout another wide area with a
thickness equal to that which the separate seams had previously maintained.
Let A-C (Figure 430) be a three-foot seam of coal originally laid down as a mass
of vegetable matter on the level area of an extensive swamp, having an under-
clay, f-g, through which the Stigmariae or roots of the trees penetrate as
usual.
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