898 aEOLOGY OF OHIO. 



The Gore Limestone, which is found from thirty to forty feet above the 

 Zoar, resembles the latter in some of its phases, and can easily be mis- 

 taken for it. Like the latter, too, it is underlain with a coal seam and 

 overlain with iron ore. As a limestone, it is chiefly found in Hocking 

 and Vinton counties. It is often replaced by flint, though seldom by as 

 heavy deposits as the Zoar horizon shows. Like that limestone, it is 

 dark blue in color, but it is not as heavily charged with fossils as the 

 Zoar. In Sections 25 and 26, Starr township, Hocking county, however, 

 it yields very perfectly preserved fossil shells. It has been used to- some 

 extent as furnace flux, but it is inferior to most of the limestones of the 

 district for this purpose. 



This, then, is the geological frame-work of the district. The main 

 elements, already named, are persistent, and can readily be distinguished 

 from each other. The accessory seams come in to facilitate the identifi- 

 cation. A careful enough examination of these elements will, therefore, 

 show the proper horizon of every portion of the field. 



The fact that the limestones already described are closely associated 

 with seams of both coal and iron ore, has already been incidentally men- 

 tioned. It is a point of so much importance that it deserves to be treated 

 at more length. 



There are four elements of the Coal Measures that are the products of 

 life, viz., seams of coal and ore, and beds of limestone and flint. The 

 last two have been found to be interchangeable to a high degree in the 

 review already made. There are, in fact, but two limestones of the main 

 series that are not very frequently leplxced by flint. Both limestone 

 and flint show their organic origin unmistakeably, being often filled 

 with remains of the marine life of the periods in which they were formed. 



It needs no argument to prove that coal is the product of ancient veg- 

 etable growths. The microscope shows in coal the various tissues that 

 belong to plants, and even enables us to estimate the relative proportions 

 of these several tissues that make up a coal seam. 



A bed of iron ore is a less obvious sign of the former presence of veget- 

 able matter than a coal seam, but it is not a less certain sign. Unlike 

 coal, iron ore is not formed from the tissues themselves, but it is accumu- 

 lated by means of such tissues. The iron that is difiused so generally 

 through rock formations of all sorts, is rendered soluble by the presence 

 and through the agency of organic matter, and by the same agency is 

 gathered into seams of carbonate of iron. 



These three or four elements are intimately associated in all our Coal 

 Measure rocks. This association recurs again and again in the series 

 under consideration. Coal, limestone or flint, and ore, mark vital nodes 

 in the series, these nodes being separated from each other by beds of 



