ties near together in the same locality. Especially if it yields 
copiously for months in succession, as often happens, without 
any material diminution in quantity, or increase of the intervals 
tween the successive yields, the rocks in its neighborhood may 
Saat to contain rich supplies of oil that may be directly 
e 
On Oil Creek in Pennsylvania the greatest quantities of oil 
are found in the same horizontal stratum of sandstone. It woul 
Seem that this rock is very porous, and perforated like a honey- 
gas (the “ breathings of the earth,” as they are called,) are to be 
explained on the same principle as before, by supposing that as 
ishing flow, until a relative vacuum is again created r which 
the influx is renewed and gradually increases as at the begin- 
’ ning. These regular alternations vary in different wells from 
two or three times a day to as many times an hour; the inter- 
: 8, however, gradually increasing in length as the supply of 
Cations are forced, and the well, deriving new supplies, starts off 
riod. It often happens that the same well 
48 two periods ;—one of variation in the flow, and another of 
Cessation, consequent on the escape of gas. : 
] Amore uniform flow may be secured by making the orifice 
___ St the mouth of the tube smaller. This is often desirable in order 
prevent the escape of gas by the exhaustion of the oil in the 
“avity down to the bottom of the boring. Sometimes such a 
= ssa will thus rush out, before the oil raised up by the water, 
<> the passage again, as not only to render the pump neces- 
0 tnpard that to raise oi], but also to diminish materially the 
tux of oil from other cavities by reducing the pressure of the 
_ 888 in them. Another expedient sometimes resorted to, when 
