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 bufE 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 Limestone. 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. 15 is so named in the general section. 



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 blw 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 vseam has been quite largely worked in the southern furnaceii 

 under a variety of names, as "Top Hill Ore" in Gallia Furnace, and also 

 in Vesuvius; as the "Burdett Or<e " on the Monitor Furnace lands. It is 



