often happens that a porous stratum, consisting of sand, sandstone,
chalk or other calcareous matter, is included between two impermeable
layers of clay, so as to form a flat [Transcriber's Note: The original
text reads 'porus'] porous U tube, continuous from side to side of
the valley, the outcrop on the surrounding hills forming the mouth
of the tube. The rain filtering down through the porous layer to the
bottom of the basin forms there a subterranean pool, which, with the
liquid or semi-liquid column pressing upon it, constitutes a sort
of huge natural hydrostatic bellows. Sometimes the pressure on
the superincumbent crust is so great as to cause an upheaval or
disturbance of the valley. It is obvious, then, that when a hole is
bored down through the upper impermeable layer to the surface of the
lake, the water will be forced up by the natural law of water seeking
its level to a height above the surface of the valley, greater or
less, according to the elevation of the level in the feeding column,
thus forming a natural mountain on precisely the same principle as
that of most artificial fountains, where the water supply comes from a
considerable height above the jet.


HOW MANY CUBIC FEET THERE ARE IN A TON OF COAL.--There is a difference
between a ton of hard coal and one of soft coal. For that matter, coal
from different mines, whether hard or soft, differs in weight, and
consequently in cubic measure, according to quality. Then there is a
difference according to size. To illustrate, careful measurements have
been made of Wilkes-barre anthracite, a fine quality of hard coal,
with the following results:

Cubic-feet Cubic feet
in ton of in ton of