890 : GEOLOGY OF OHIO. 
Limestone may be named as a very wide spread and persistent seam. It 
takes its name from Ewing Site, in the Sunday Creek Valley, where it is 
a ferruginous limstone, five feet in thickness, about eighty feet above the 
Cambridge and forty feet below the Ames. It holds its place throughout 
the counties southward to the Ohi» River, and by its steadiness, indeed, al- 
most deserves to be counted in the first list. It weathers easily and is so 
often hidden by the products of its own decomposition that it escapes 
general notice. 
These, then, are the principal limestones at present known in the 
Hanging Rock District. They constitute a very orderly and symmetrical 
system. The suggestion of Croll, that the Coal Measures are the product 
of a glacial period, the coal seams themselves, and equally the lime- 
stones and ores with which they are associated, being interglacial 
growths, finds ia this series its best illustration, and, perhaps, furnishes 
the best explanation of the astronomical regularity with which these 
horizons succeed each other. ) 
Hach of the limestones named will be briefly described. 
1. The Muxville or White Limestone—It is harder to characterize the 
Maxville limestone than any other in the series. The exposures of it 
are few in number, and even these few exhibit great diversity of com- 
position. The most valuable and, on the whole, the most characteristic 
part of the stratum as seen at Maxville, Perry county, at Winona 
Furnace, and at Logan, Hocking county, consists of a light drab- 
colored limestone, very fine grained and homogeneous, generally poor 
in fossils, breaking with a conchoidal fracture and looking very like 
lithographic stone. Other portions of the stratum are blueish in color, 
and others still are colored green by silicate of iron. There is often 
a notable quantity of this substance in the clays that are found be- 
tween the layers of the limestone. <A light blue stone that is found 
at the Winona Furnace drifts, is equal in quality to the portion already 
described. It greatly resembles in appearance the famous Dayton Lime- 
stone of Upper Silurian Age. The drab or white limestone yields at 
its best over ninety per cent. of carbonate of lime, and is much esteemed © 
as furnace flux. The darker beds are generally rejected by the furnaces 
as too silicious, but analysis shows that selection cannot properly be 
made on the ground of color. 
Tt has already been stated that this formation is unsteady and irregular 
in its occurrence. The best guide in following it is the persistent and 
easily recognized horizon of the Zoar or Blue Limestone, which, with its 
blo:k ores, is universally known throughout the district. The place of 
the Maxville is about one hundred feet below the Blue Limestone. The 
