SUPPLEMENTAL KEPOKT — HANGING, ROCK DISTRICT. 



counties ; but inasmuch as the Zoar or Blue Limestone, which is also 

 found in this district, is equally with the Gray Limestone, ferriferous, 

 this designation will be replaced here by a geographical name. As this 

 limestone is everywhere developed and everywhere known throughout 

 the Hanging Eock District, and is almost the sole reliance of all the 

 southern furnaces for flux, it will be styled the Hanging Rock Limestone. 

 It is ordinarily known as the Gray Limestone. It is the duplicate of the 

 Gray Limestone of the eastern counties. This last seam, it will be re- 

 membered, received from Prof. Andrews the name of Putnam Hill Lime- 

 stone, fi-om a fine exposure opposite Zanesville. As the Putnam Hill 

 Limestone is followed westward, it is found to grow thin and finally dis- 

 appear. It is in good force as a flint and lime horizon at New Lexington, 

 Perry county — being'shown in a section of five feet in the railroad cut, 

 just ea!?t of the station, but it cannot be followed, without change, far 

 beyond this point. It seems to become an ore horizon to the southward. 

 The " Limestone Kidney" ore of the southern counties lies very near its 

 proper place. A bastard limestone is found associated with this ore seam 

 at McCuneville and elsewhere. But just as the Putnam Hill Lime- 

 stone fails, a new one makes its appearance. In the neighborhood of 

 Bristol, Perry county, a horizon of lime, flint, and ore appears from fif- 

 teen to thirty feet above the Putnam Hill Limestone. Its usual distance 

 is a little more than twenty feet. It, too, is a gray limestone, and it takes 

 its place in a series of fifty or sixty feet of strata that repeat, in a remark- 

 able way, the order of the strata found with the Putnam Hill Limestone. 

 It will be remembered that the Zoar or Blue Limestone very often occurs 

 in the district in two courses, from fourteen to twenty-two feet apart. 

 As this interval is sometimes wholly filled with fossiliferous, calcareous 

 shales, and as the limestones indicate the same conditions of growth, 

 there can be no question as to their both belonging to the same epoch ; 

 and they are, therefore, distinguished as the Upper and Lower Zoar 

 Limestones. It will be hereafter shown that the Cambridge Limestone 

 is split in the same way, its two courses being separated by intervals 

 varying from one to twenty-seven feet, and the separate courses being 

 known as Upper and Lower Cambridge. There is almost equal warrant 

 for counting these two gray limestones as belonging to one epoch, and 

 giving them the game general name. The difi'erence between the cases 

 does not lie in the magnitude so much as in the character of the inter- 

 vals. The Putnam Hill and Hanging Rock horizons are separated in 

 the northern part of the field by sandstones which indicate a more com- 

 plete break than is shown by the fire-clays and fossiliferous shales re- 

 ferred to above. The Hanging Rock Limestone will accordingly be 

 treated by itself in- the following review. 



