do 2 TRANSACTIONS OF THE AMERICAN INSTITUTE. 



But if the gas reaches its equilibrium with the hydrostatic pressure before 

 the oil is reduced so low, we may theu pump out oil till the water rises in 

 the mouth of the tube, after which mixed oil and water will be obtained 

 until the supply is exhausted, provided the pump is of sufficient power to 

 paevent interruptions from the too rapid rise of the water. 



3. Suppose the boring strikes the cavity at a still lower point and enters 

 the water. If the gas has sufficient tension, water is raised until its level, 

 in the cavity, is below the end of the tube; then mixed oil and water is 

 obtained, and afterwards pure oil, when the same conditions follow as in 

 the second case. Sometimes the pressure of the gas will raise the water 

 only a part of the way up the boring, and yet the well will be found pro- 

 ductive. The Shattuck well, on the Little Kanawha river, had to be 

 drained of water, with a steam pump for two weeks before oil was obtained, 

 but afterwards it yielded abundantly. 



Some varieties of action are to be accounted for on the supposition that 

 there are in the same cavity different collections of gas separated by a 

 partition from the top. 



Intermittent or Replenished Wells. 



This class exhibit the same phenomena as the first, but as often as they 

 are exhausted are replenished again and repeat a certain series of actions 

 indefinitely, and with considerable regularity of tiuie. This is to be ex- 

 plained by supposing they are connected with other reservoirs, b}'' slight 

 channels of communication whose capacity for replenishing is less than that 

 of the tube for exhausting. The Newton well, on a branch of the Little 

 Muskingum, a few miles from Marietta, belongs to this class. It repeats 

 its process, at regular intervals of about a half an hour, expelling about a 

 barrel of oil each time. When the well stops, it is necessary to pump out 

 a little water, in order to start it again; then the oil rises spontaneously. 

 A column of oil will be raised, by a given pressure, so much higher than 

 the column of water as its specific gravity is less. In this case, the specific 

 gravity of water being to that of oil as 1000 to 816, the coluum of oil will 

 be about one-fourth higher than the column of water. This difiercucc is 

 •sufficient to make it flow over the top of the tube. 



Wells on Oil Creek, Pennsylvania. 



Here the greatest quantity of oil is found in the same horizontal stratum 

 of limestone. It would seem that this rock is very porous and penetrated, 

 like a honey comb, with numerous cells and fissures containing petroleum. 

 In most of the wells here there is an increase and diminishing of the force 

 of gas at regular intervals, but without any cessation of force for a long 

 time. These variations are called the "breathing of the earth." The 

 regular alterations vary in different wells, from four or five times a day to 

 as many times an hour. The intervals gradually increase in length as the 

 supply of oil diminishes; unless, as sometimes happens, new communica- 

 tions arc forced, and the well, deriving new supplies, starts off again with 

 a new period. It often happens that some wells has two periods-; one of 

 variation in the flow, and another of cessation, consequent upon the escape 

 of gas. It is not an uncommon thing for an intermittent well to throw 



