ECONOMIC GEOLOGY OF OHIO. 
OleleaJjediialgs It 
THE STRATIGRAPHICAL ORDER OF THE LOWER COAL 
MEASURES OF OHIO. 
By Epwarp ORTON. 
The classification of the coal measures of the Northwestern portion 
of the Appalachian field, which was proposed by Henry D. Rogers in 
the reports of the First Geological Survey of Pennsylvania (vol. LI, 
part I, p. 16), has been accepted and followed, at least in its main fea- 
tures, by all of the geologists that have subsequently worked in the ter- 
ritory to which this classification applies. 
Rogers recognized five sub-divisions or sub-formations of the rocks 
of this series, and to these divisions he assigned the following names, 
VIZ. : 
Upper Barren Measures. 
Upper Coal Measures. 
Lower Barren Measures. 
Lower Coal Measures. 
Seral Conglomerate. 
FS Ss 
To the lowest sub-division, viz., the Conglomerate, a thickness of 
500 feet was assigned in Western Pennsylvania, to the Lower Coal 
Measures, a thickness of 600 feet ; to the Lower Barren Group, a thick- 
ness of 500 feet ; to the Upper Coal Measures, 250 feet, and to the Up- 
per Barren Group, 950 feet. 
The vertical boundaries of the several groups were quite defi- 
