THE IRON ORES. 379 
1. Upper Freeport coal.—Main blackband horizon. Also, clayband ores.. 
2. Forty feet below Lower Mercer limestone.—Confined to Southern Ohio. 
“Flag ore,” Boggs ore.” 
3. Sharon coal.—Blackband ore; mainly in Northern Ohio. 
There are local deposits of blackband or other stratified ores out- 
side of these horizons, but no really valuable beds have yet been found 
among them. Some of these local accumulations will be noticed on 
subsequent pages. It is not probable that any persistent horizons of 
iron ore have been missed in the Lower Measures, but we may reason- 
ably expect, through accumulating skill, to be able to work at some 
future time beds that we now reject, and there is good reason, also, to 
believe that many valuable basins of ore remain to be discovered at 
the several horizons named above. 
Il. THE CONCRETIONARY ORES. 
a. The Kidney Ores. 
These ores as now worked are derived from the several horizons 
named below: 
Upper Freeport limestone—In Southern Ohio. 
Lower Freeport limestone—In Southern Ohio. 
Kittanning shales—Between Kittanning coals. 
Ferriferous limestone and Clarion coals. 
Putnam Hill limestone—In Southern Ohio. 
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6. The Block Ores. 
The ores of this class are derived from the several horizons named 
below: 
Putnam Hill limestone—In Northern and Central Ohio. 
Upper Mercer limestone. 
Mercer shales—Between Mercer limestones. 
Lower Mercer limestone. 
Maxville limestone—Sub-carboniferous. 
EX GS $9 89 
ce. The Lnmestone Ores. 
The limestone ores are referable mainly to one horizon, viz., that 
of the Ferriferous limestone. There is in reality but one ore from this 
