BITUMINOUS COAL STRATA. 247 
slightly resembling the flutings on some ornamen- 
tal columns. But, in proof of this, reference need 
only be made to the aquatic vegetables which are 
found on the surfaces of some of the layers, and 
which were apparently entombed in the place of 
their growth. 
IV. Resting on the alternations of sandstones and 
shales, occurs a stratum (E) which was formed un- 
der conditions widely different from those which 
prevailed during the deposition of the strata which 
have been mentioned. It consists of coarse sili- 
cious sandstone and conglomerate, both of which 
frequently pass into each other, according to the 
variable velocities of the waters in which the mate- 
rials were deposited. That part of the stratum 
which is conglomerate is composed principally of 
quartzose sand and pebbles, the latter of which are 
variable in size, from a pea to two or three inches 
in diameter. These materials are partially miited, 
sometimes with iron, and at others, it would ap- 
pear, merely by adhesion ; the pebbles are rounded 
by attrition, and strongly resemble shingle on the 
seashore. These pebbly materials were doubtless 
deposited by currents of water of unequal veloci- 
ties, but sufficiently strong to move them onward 
and distribute them over an area of vast extent, 
leaving the sand in one place, the gravel in another, 
and the coarse pebbles in another, and so on ; thus 
producing the various changes which we now ob- 
serve, and causing the stratum, even in short dis- 
tances, to pass from sandstone to fine conglomerate, 
and from the latter to one very coarse in its tex- 
ture. This deposite was probably made in the vi- 
cinity of dry land, as near its junction with the 
strata of the third division are found the remains of 
a few terrestrial vegetables. 
V. Superincumbent upon the conglomerate is a 
series of deposites (F), which indicates another im- 
portant era or change. In the preceding period 
