BLENDING OE COAL-SEAMS. 
401 
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 pres¬ 
ence 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-inter¬ 
mixture of sediment, or of clay, sand, and pebbles, with the 
pure coal wholly unexplained. 
The late Mr. Bowman was the first who gave a satisfac¬ 
tory 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 previ¬ 
ously maintained. 
Fig. 430. 
E 
C 
Uniting of distinct cocil-sCcims. 
Let A C be a three-foot seam of coal originally laid down 
as a mass of vegetable matter on the level area of an exten¬ 
sive swamp, having an under-clay, f through which the 
Stigmariae or roots of the trees penetrate as usual. One 
portion, B C, of this seam of coal is now inclined; the area 
of the swamp having subsided as much as 25 feet at E C, 
and become for a time submerged under salt, fresh, or brack¬ 
ish water. Some of the trees of the original forest ABC fell 
down, othei’S continued to stand erect in the new lagoon, their 
stumps and part of their trunks becoming gradually envel¬ 
oped in layers of sand and mud, which at length filled up 
the new piece of water C E. 
When this lagoon has been entirely silted up and convert¬ 
ed into land, the forest-covered surface A B will extend once 
more over the whole area A B E, and a second mass of veg¬ 
etable matter, D E, forming three feet more of coal, will ac¬ 
cumulate. We then find in the region E C two seams of 
coals, each three feet thick, with their respective under-cla 3 ^s, 
with erect buried trees based upon the surface of the lower 
coal, the two seams being separated by 25 feet of interven¬ 
ing shale and sandstone. Whereas in the region A B, where 
the growth of the forest has never been interrupted by sub¬ 
mergence, there will simply be one seam, two yards thick, 
corresponding to the united thickness of the beds B E and 
