Geography of Ohio 167 



theory" of oil and gas. This explanation arose doubtless from 

 the frequency with which paying wells occur in the upper parts of 

 anticlines or near the axes of benches and terraces. In the Tren- 

 ton limestone field, the wells seem to follow the axis or keep near 

 the axis of the Cincinnati arch. Even beyond the zone of the 

 pronounced anticlinal fold, where the formation contains only a 

 bend or bench, paying wells are generally confined to the terrace. 

 Elsewhere in the state, profitable drilling has disclosed a similar 

 arching of the formations. This coincidence of paying wells and 

 disturbed areas in the rocks has suggested the '' anticlinal theory" 

 of the occurrence of oil and gas. This theory states that since 

 oil and gas are lighter than water, they seek the higher parts of 

 formations which are not horizontal, the oil overlying the water 

 and the gas capping the oil. The influence of gravity would 

 account for such a distribution of these substances. 



OEIGIN OF OIL AND GAS 



These valuable resources are not found e\'erywhere. While 

 they occur in geological horizons that differ much in age, they do 

 not occur in all parts of any one formation. It has been demon- 

 strated that the oil producing area of the Trenton limestone in 

 this state is localized. The only formation which appears to 

 have even a general distribution of oil and gas is the Berea, but 

 the Berea does not in all places bear these fuels in commercial 

 quantities. 



The fact that both oil and gas are usually found together, gas 

 always with oil, implies something common in their origin. Gas 

 sometimes occurs without oil, but in gas territories oil is occasion- 

 ally found. Petroleum gives off a gas that closely resembles natural 

 gas. Furthermore, in areas producing both, if anything unusual is 

 found in the composition of the one, the same peculiarity generally 

 characterizes the other also. As an illustration, the Trenton lime- 

 stone produces both oil and gas in each of which there is some 

 sulphur; but if, in a particular section, the sulphur is lacking in 

 one, it is absent also in the other. These, and several other rea- 

 sons, lead us to believe that oil and gas have a common origin. 



These fuels belong to the hydrocarbon group of natural pro- 

 ducts. The principal elements in them are hydrogen and carbon. 

 With these hydrocarbons usually occur several of their deriva- 



