THE OIL- AND GAS-PRODUCING ROCKS OF OHIO 829 



of the country, and when it dips beneath the surface it becomes 

 the repository of invaluable supplies of petroleum, gas, and salt 

 water." " 



The composition and structure are very constant. The color 

 is gray below drainage, but has a tinge of yellow above. The 

 sand is of moderate fineness, and composed almost wholly of 

 silica. Occasionally it contains carbonate of lime, probably as 

 a cement, but this never constitutes more than a very small frac- 

 tion of the formation. That found below the surface around the 

 village Berea in Cuyahoga county is undistinguishable from that 

 obtained at a depth of more than 2,000 feet in Washington 

 county. Sometimes, though not usually, the formation divides, 

 a bed of shale lying between two of sandstone ; at other places 

 the upper portion of the formation consists of sandstone and the 

 lower of shales. In thickness the formation varies from 50 feet 

 or more in the northern part of the state to a half dozen or less 

 in the southeastern portion, and occasionally disappears entirely, 

 its place being occupied by shales. The Berea grit is succeeded 

 above by the Berea (Sunbury) and Cuyahoga shales, having 

 usually an aggregate thickness of from 500 to 600 feet, and 

 below by the Ohio shales, having a great and rapidly increasing 

 thickness eastward. The most remarkable character of the 

 formation, however, remains to be mentioned, viz., its persist- 

 ence. From its outcrop it has been followed by the drill from 

 county to county, and often from section to section, until the 

 eastern and southeastern limit of the state is reached. It is as 

 easily recognized below drainage as above, and this character 

 makes it a stratigraphical landmark of great value to both driller 

 and geologist. In many counties in the eastern part of the state, 

 especially those fronting on the river, numerous efforts have been 

 made to find a productive sand below the Berea, but in every 

 case this effort has been unsuccessful. It may now be taken as 

 having been demonstrated by the drill that when the Berea sand 

 has been passed in this territory the last hope of oil or gas has 

 gone. 



While a trace of oil or gas has perhaps been found in every 



1 Ibid., Vol. VII, p. 28. 



