908 GEOLOGY OF OHIO. 
and Ironton would be proof of difference of age rather than of equivalence, 
in most parts.of the Coal Measures, but there is such unusual steadiness 
in this district that there is reason for believing these horizons to be the ~ 
same. The question can be settled by a little more work in Vinton and 
Jackson county. 
No limestone is found at this horizon south of Jackson county. It will 
be remembered that the limestone where it does occur is called the 
Norris limestone from its contiguity to the coal of that name. The ore 
seam for the same reason is termed the Norris ore and is so represented 
in the section. 
13. An ascent of twenty-five to thirty feet above the Norris limestone 
and ore—or of sixty-five to seventy feet above the Great Vein Coal (No. 
VI) brings us to another buff limestone and an accompanying ore, the 
latter of which has been worked to some extent in Perry county. The 
limestone is largely used for flux in the new furnaces at Shawnee and 
has, therefore, been named in this report the Shawnee Inmestone. The ore 
would naturally be called from its association the Shawnee ore but con- 
fusion would be sure to result from such a designation, the ore seam 
which is the sole reliance of the Shawnee furnaces belonging to a distinct 
horizon. | 
This seam has been worked for ore at various points in the Hocking 
Valley, notably at Straitsville, within the last few months, where several . 
thousand tons have been raised. Its best designation, then, will be the 
Straitsville Ore. It is so named in the general section. Maids 
The volume of the ore is large, and the percentage of iron in the out- 
crop is generally satisfactory, but its association with the limestone that 
bears it is somewhat different from that observed in the lower ores. It 
will be noticed that buff limestones occur again and again in the one 
hundred and fifty feet of strata that overlie Coal No. VI, while in the same — 
number of feet below this coal seam, the limestones are all blue in color. 
These upper ores pass by gradations into the limestones, so that while 
the outcrop is an ore of excellent character, it may soon change under 
cover to a ferruginous limestone, containing possibly but ten or fifteen 
per cent. of iron. This is true of the Straitsville Ore throughout the 
Hanging Rock district. While the blue limestones are often ferruginous, 
there is a much better distinction between them and the ores which they 
bear, than is found in the “case of the buff limestones now referred to. 
Complete substitution of the blue limestones by ore can often be noticed. 
This seam has been quite largely worked in the southern furnaces 
under a variety of names, as “Top Hill Ore” in Gallia Furnace, and also 
in Vesuvius; as the “Burdett Ore” on the Monitor Furnace lands. Itis 
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