In the
neighborhood of Pittsburgh, this is usually found at a depth of 1,300
to 1,500 feet, in what is known as the Third Oil Sand, a sandstone of
the Devonian period. Where the gas comes from originally is an open
question. When the driller strikes gas, he is not left in any doubt of
the event, for if the well be one of any strength, the gas manifests
itself by sending the drill and its attachments into the air, often
to a height of a hundred feet or more. The most prolific wells are
appropriately called "roarers." During the progress of the drilling,
the well is lined with iron piping. Occasionally this is also blown
out, but as a rule the gas satisfies itself with ejecting the drill.
When the first rush of gas has thrown everything movable out of its
way, the workmen can approach, and chain the giant to his work. The
plant at the well is much simpler than one would suppose. An elbow
joint connects the projecting end of the well piping with a pipe
leading to a strong sheet-iron tank. This collects the salt water
brought up with the gas. Ordinarily, about half a barrel accumulates
in twenty four hours. A safety valve, a pressure indicator, and a
blow-off complete the outfit. When the pressure exceeds a prescribed
limit, the valve opens, and the gas escapes into the blow-off. This
is usually 30 feet high or more, and the gas issuing from the top is
either ignited or permitted to escape into the atmosphere. The
pipe line leading from the tank to the city is of course placed
underground.
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