56 GEOLOGY OF OHIO. 



very common use to which it was here applied. It was used, not because 

 it was counted superior in any way, in quality, to the drift clays that were 

 worked with it, but because it was obtained with less trouble and expense 

 than they. It cannot reasonably be expected to bear high heat without 

 melting, on account of the large amount of lime in its composition. 



The same line of remarks would apply to the numerous beds of shale 

 that occur in the Hudson River formation, which directly underlies the 

 Medina shale. There are about eight hundred feet of this formation 

 shown in the state and its outcrops occupy six thousand square miles of 

 our territory. The upper part of the formation is rich in shale, beds of five, 

 ten, or fifteen feet of it frequently occurring interstratified withthelimestone 

 sheets. No instance is known, however, in which an attempt has been 

 made to turn these calcareo-argillaceous beds to economic use, The 

 latter are marls rather than shales. A similar line of facts is also found 

 in certain argillaceous deposits of the Clinton and Niagara divisions of 

 our shale. At the top of the first named series of beds a very fine-grained 

 deposit of bluish-white clay occurs. It is locally known as the Clinton 

 marl, Beavertown marl, etc. Calcareous fossils are distributed through 

 it. The marl is but one to four feet in thickness. If there were more of 

 it, it is possible that some use could be found for it, since the fineness of 

 grain is unusual. 



The Niagara shale (6a of the scale above given) is another of these 

 calcareo-argillaceous deposits that deserve the name of marls in part, at 

 least, of its extent, rather than of shale, There is a large body of this 

 formation, its maximum thickness, which is reached in Adams County, 

 being a full one hundred feet. In so considerable an extent there must 

 also be considerable range in quality, and it seems by no means unlikely 

 that some parts of the Niagara shale will prove well adapted to use in 

 clay working o some sort. 



The next formations that deserve mention in this list are numbers 

 nine and ten of the scale, viz : the Hamilton or Olentangy and the Ohio 

 shale, respectively. The Hamilton (No. 9) has no where been worked as 

 a basis of clay manufacture and does not seem likely to be. There are 

 but few outcrops of it tf> be found and what there are give no promise of 

 special adaptation to practical uses. This stratum has a thickness of 

 fifteen or twenty feet only. 



It is somewhat different with the Ohio shale (No. 10), at least so far 

 as its possibilities are concerned. This is a great formation, ranging in 

 its outcrops between two hundred and fifty and four hundred feet in 

 thickness. Under cover, as it is followed to the eastward, it is continu- 

 ally strengthened until on the Pennsylvania border it has been proved by 

 drilling to be more than two thousand five hundred feet thick. Its out- 

 crops are of large extent, occupying a belt ten to twenty miles wide that 

 reaches entirely across the state from north to south. 



