2 History of Anthracite Coal in Nature and Art. (January, 
ern deltas. That the wood and fine sand exist without pebbles, 
and are stratified with the leaves and roots of terrestrial plants, 
free in most part from any intermixture of marine remains, im- 
ply the persistence in the same region of a vast body of fresh 
water. This water was also charged, as is a great river, with an 
inexhaustible supply of sediment, and such as would drain a con- 
tinent having within it one or more ranges of mountains. A bed 
of coal, even when purest, consists of distinct layers, though not 
usually separable unless quite impure from the presence of clay. 
These layers may,be distinctly seen as alternating shades of black, 
even in almost any of the hardest specimens of anthracite. The 
researches of chemists have proved’ that wood burned in the 
earth and exposed to moisture and partially or entirely excluded 
from the air, is converted into lignite or brown-coal. A long 
period of decomposition finally changes this lignite into bitumin- 
ous, and subsequent decarbonization through the increased heat 
of pressure or proximity to the heated earth, converts this finally 
into anthracite. The gases that result are the fire damp so de- 
structive to incautious miners. 
The processes through which the beds of anthracite has passed 
may be outlined as follows; 
The coal was formed at the level of the sea and afterwards 
lifted to a vast height, but the shrinking and crumpling of the 
crust has flexed these beds and the many sand and clay and lime- 
stone beds beneath them; the frost and rains have broken them 
down and the waves of the ancient sea have repeatedly rolled 
over them as they have many times subsided to be again raised 
and again acted upon by agencies above the water. But a small 
part of these coal beds, and of the great masses of rock which 
once towered to such vast heights, remain, and the greater the 
elevation the greater has been the destruction. Our beds of an- 
thracite are now found only where the subsidence was very great 
—in troughs caught in foldings of the underlying rocks, being 
often nearly vertical and doubled and re-doubled upon each other. 
The old rocks were worn down, after the once horizontal deposits 
had been made to stand on edge at various angles to the horizon; 
the soft clays and limestones and sands were then washed into 
the ocean, or gathered into the deeper depressions in the con- 
torted strata. 
The Carboniferous ead opened with a marked change over 
