Mar., 1910.] Pennsylvanian Limestones. 93 



In 18S4 Dr. Orton in a discussion of the " Stratigraphical 

 Order" gives the fullest account of the Lower Coal Measure 

 Limestones yet to appear. He here correlates the Gore Lime- 

 stone with the Upper Mercer of Pennsylvania and regards the 

 limestone found between the Lower Mercer and Putnam Hill in 

 the different counties as identical with the Upper Mercer. He 

 states that: 



"It everywhere lacks the remarkable steadiness and contin- 

 uity of the Lower Mercer, but in all other respects it is almost 

 the exact counterpart of that well-marked stratum. It has, in 

 the main, the same chemical composition, the same color, and 

 other physical properties, and also the same fossils. In many 

 instances the limestones can be distinguished only by their 

 stratigraphical order." [Ohio Geol. Sur. Vol. V, p. 15.] 



In discussing the Ferriferous Limestone, Dr. Orton says of it, 



" * * * * there are still unsettled questions as to its westward 

 extension through a number of counties." 



"From the eastern side of Mahoning County, to the center of 

 Perry County, the Ferriferous Limestone is either feebly devel- 

 oped and obscure or is altogether wanting. But in this very 

 interval where the Ferriferous Limestone has grown weak and 

 uncertain, another limestone of the same general character is 

 found, which completely bridges the chasm and by means of 

 which we are able to maintain the unity of the series unbroken. 

 This is the Gray limestone of Newberry and the original Putnam 

 Hill of Andrews." 



" * * * * The Putnam Hill limestone underlies the Ferriferous 

 by 15 to 50 feet. The usual interval may be counted 30 feet. 



" * * * * The Putnam Hill limestone is from 25 to 50 feet above 

 the Upper Mercer Limestone ****." [Ohio Geol. Sur. Vol. V, 

 pp. 19-21.] 



In a report in 1906 dealing with the limestones of Ohio, Ed- 

 ward Orton, Jr., and S. V. Peppel review these Coal Measure 

 Limestones and make the following statement regarding the 

 Putnam Hill: 



"It is very close, stratigraphically, to the Ferriferous Lime- 

 stone, a very important bed. The area occupied by the two does 

 not overlap, so far as the knowlegde of the writers extends. At 

 the point where the Ferriferous is present, the Putnam Hill is 

 not likely to be found, and vice versa. Both stones lie close below 

 the Lower Kittanning or No. 5 coal, but they are probably strati- 

 graphically distinct." [Ohio Geol. Sur. Vol. IX, Bull. 4, p. 173.] 



Of the Ferriferous Limestone, the same writers state that: 



"In stratigraphical position, the Feniferous belongs a short 

 distance above the Putnam Hill Limestone and from twenty to 

 forty feet below the Lower Kittanning coal. This places it near 

 the bottom of the Allegheny formation. 



