BITUMINOUS COAL MEASURES. 245 
Bituminous Coal Measures, 
These differ chiefly from the anthracite coal meas- 
ure in containing more frequent beds of limestone, 
marl, clay, and, perhaps, iron ore. 
We cannot present a more intelligible view of the 
bituminous coal measures of the United States, than 
by giving the following Section of the Carboniferous 
System of Ohio, by Lieut. Mather. 
Fig. 44. 
:H Upper coal series. 
G Calcareo-silicious rock. 
F Lower coal series. 
»{*^'/;;SE Conglomerate. 
300|f^§0; 
^}<^^i^^iP Waverley sandstone series. 
C Slaty argillaceous rock, con- 
taining pyrites, &c. 
Great limestone deposite. 
" For convenience of description," says Mr. Briggs, 
the above strata have been separated into seven 
groups or subdivisions, which, it is believed, corre- 
spond with important eras or changes during this 
deposition." 
I. The first subdivision (marked B) includes the 
limestone of Adams and Highland counties, and is, 
probably, merely a continuation of that which forms 
the rocky strata of the whole western portion of the 
state. This limestone is of great thickness, and 
contains, where it has been examined, the petrified 
exuviae of radiated and molluscous animals of ma- 
rine origin, some of which belong to extinct genera, 
X 2 
