SOMETHING ABOUT OIL. 



285 



Fig. 89. Two Oil Wells. 

 a. A blowing well. b. A flowing well. 



tinue, however, until the cavity is exhausted of its oil, after 

 which pumping will be of no avail. If the confined gas at- 

 tains its equilibrium before the oil has been completely 

 forced from the cavity, it is evident that the remainder 

 must be obtained by pumping. There is no cavity so large, 

 however, as not to be destined to ultimate exhaustion. 

 Every oil well, of whatever class, is destined to abandon- 

 ment. It is true that Nature is constantly at work replen- 

 ishing the exhausted reservoirs, but her accumulations are 

 slow. Her working days are centuries. 



Intermittent wells appear to act in some cases precise- 

 ly after the manner of intermittent springs. More fre- 

 quently, however, it is manifest that the combined action 

 of gas and oil produces the phenomenon. In boring a 

 well, suppose a stream of gas is struck one hundred feet 

 from the surface of the rock, and a small stream of oil 

 twenty feet below the gas. The entrance of oil fills twen- 



