8 RESOURCES OF TENNESSEE. 



latter case, the hard rock layers occur in the ridges, and the soft 

 ones in the valleys. 



Angle of the rock beds. Folded rock beds may stand at any 

 angle from near the horizontal to the perpendicular. The 

 most desirable position for oil or gas is the one near the 

 horizontal. This, for the reason that the lower the dip the 

 wider the anticline and consequently J;he larger the field; and 

 for the further reason that it is easier for the driller to put 

 down a straight hole in rocks of low than of high dip. If the 

 rocks dip as much as 20 degrees, it is difficult to drill a straight 

 hole, especially if they consist of alternating beds of shale and 

 sandstone or other hard rock. When the drill passes through 

 a soft bed and strikes a high-dipping hard one, the tendency is 

 for the bit to slip downward over the hard surface, and turn 

 the hole away from the perpendicular. Yet, with care, an 

 experienced driller can put down a straight hole in alternating 

 beds of sandstone and shale that dip 20 degrees, or even more. 



Horizontal reservoirs. There are reservoirs that consist of 

 lenses of sandstone lying horizontal or nearly so, sealed up in 

 beds of shale. In such cases, neither the geologist nor the 

 driller can locate the reservoir, without drilling. It follows that 

 the striking of such reservoirs with the drill is a matter of 

 chance; and after such a reservoir is struck, its size can be 

 determined only by the driller. 



THE CENTRAL BASIN. 



It is for the double purpose of preventing further loss from 

 what geologists believe is a hopeless quest for oil and gas in the 

 Central Basin, by those who might in the future make the ven- 

 ture, as others have done in the past, and put down wells with- 

 out geological advice ; and for answering the question that fre- 

 quently comes from those who are more cautious, as to whether 

 oil and gas occur within the Central Basin, that this paper is 

 written. 



Enticements to prospecting In the past, more or less interest 

 has been aroused in many parts of the Central Basin over oil 

 and natural gas. In places this has resulted in the expenditure 

 of money by drilling wells from a few score to a few hundred 



