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 united, 

 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 



