nge of this
inclination produces a series of waves, the crests of which are known
as anticlines, and the troughs as synclines. Many drillers suppose
that the gas seeks the anticlines and the oil the synclines, but
others, equally long-headed, discard entirely all theory of this kind,
and drill wherever it may be most convenient or where other operators
have already demonstrated the existence of gas. It will surprise many
of our readers to know that the divining rod, that superstitious relic
of the middle ages, is still frequently called upon to relieve the
operator of the trouble of a rational decision. The site having been
selected, the ordinary oil-drilling outfit is employed to sink a
hole of about six inches in diameter until the gas is reached. 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. Beyond a little wooden house, the blow-off, and a
derrick, the gas farms differ little in appearance from those
producing less valuable crops. The pressure of the gas at the wells
varies consi