ORIGIN AND DURATION OF PETROLEUM. 279 



case, the cavity was filled with high-pressure oil- vapor 

 straining to escape. If the bore-hole tapped the crown or 

 highest curve of the roof of such an oil-cavern, it opened 

 directly into the vapor there accumulated, and the vapor 

 itself rushed out with such force that a pillar of fire was 

 raised in the air if a light came within some yards of the 

 orifice. We are told of heavy iron boring-rods that were 

 shot up to wondrous heights and we may believe these 

 stories if we please. 



If the bore-hole struck lower down, somewhere on the 

 sloping sides or in the shallow lower branches of the oil- 

 cavern, it dipped at once into liquid oil, and this oil, being 

 pressed by the elastic vapor of the upper part, was forced 

 up as a jet of spouting oil. 



In either case these violent proceedings soon came to 

 an end, for as the vapor or oil poured out, the space above 

 the oil-level where the vapor had been confined was 

 increased, and its pressure diminished, till at last it barely 

 sufficed to raise the oil to the surface, afld afterwards failed 

 to do that. 



It is quite clear from this that the supplies are not 

 " inexhaustible." The quantity of vapor having been 

 limited, there must also be a limit to the quantity of oil 

 giving off this vapor; the space in the oil-cavern occupied 

 by this vapor having been limited, there must be a limit to 

 the space occupied by the oil. The quantity of oil may be 

 ten times, a hundred times, a thousand times,or ten thousand 

 times, greater than that of the vapor, but in either or any 

 case it must come to an end at last, sooner later. 



If there were but a few wells here and there, as at other 

 similar places, such as Rangoon, the Persian oil-wells, etc., 

 the pumping might continue for centuries and centuries; 

 bnt this is not the case in America. The final boundaries 

 of the oil-bearing strata may not yet have been reached; 

 but so far as they are known they are riddled through and 

 through, and pumped in every direction, so that the end 

 must come at last, though with our present knowledge we 

 cannot say when. 



We can, however, say how it must come. It will not be 

 a sudden stoppage, but a gradual exhaustion indicated by 



