The Prince George's enquirer and southern Maryland advertiser. (Upper Marlborough, Md.) 1882-1925, 1903-03-06
THE MOTIONS OF UNDER
GROUND WATERS.

of the U. S. Geological Survey, gives
the "Amcrican Farmer" an advance
report from the department touching
the motions of underground waters.
1t is exceptionally interesting. The
report says:
The amount of water within the
crust of the earth, says Prof Charles
S. Slichter, in a paper entitled "The
Motion of Underground Waters" re-
Gently published by the United States
Geological Survey, ''is enormous,
amounting to $4,000 million cubic
yards" His estimation is based upon
the supposition that the average depth
which waters can penetrate beneath
the surface in six miles below land,
and five miles below the ocean floor.
Ills vast accumulation, if placed upon
the earth, would cover its entire sur
face to uniform depth of from 5000
to 3 500 feet. Under the influence Of
gravitatlon the water is generally in
motion, and the object of Professor
Slithter's paper is to describe the late
and manner of its overflow and the
laws governing the same. Expert
ments have shown that not do sands
and gravels possess porosity, but rocks
presumably solid and compact may be
traversed by water. Even so hard a
rock as Montello granite, selected for
the sarcophagus for the tomb of Gen.
eral Grant, on account of its great
strength, shows porosity of 023 per
cent. Tue most productive water
bearing rocks, however, are found to
be the porous stand stones, and in some
cases limestones, whose inner texture
has been chemically dissolved.
The popular idea of underground
waters is derived from the rivers of
copious dischage found in the Man,
moth and other caves. But this idea
is erroneous, as such streams, though
of great local Importance, are compar-
atively rare. The great mass of
ground water slowly percolates
through sand and gravel deposits,
sandstone, and other porous material
under a wide extent of territory
Though its motion carries it but a
fraction of mile in year, this ground
water is so widespread and often so
accessible as to he OF the greatest econ
omic Importance.
The rate Of movement of tue under
flow has been the subject OF long and
careful investigation. TO determine
this interesting question measurements
have been made in the river gravels of
streams whose surface flows have
ceased, and from such measurements
more or less trustworthy results have
been obtained. One of the most accu-
rate and interesting of these is a Sc
ries of experiments conducted by Pro
fessor Slichter along the valley of the
Arkansas river in western Kansas.
The method is an electrical one. A
double row of inch and quarter drive
wells is sunk across the chancel of the
river whose underfow is to be tested.
The upstream wells are then charged
with strong electrolyte, which dis
solves and passes down the stream
with the moving water. The passage
of the electrolyte toward the lower
we'll is shown by the gradual move
m Mt Of he needle of an electrical in
s.ralnent, and The final arrival at the
we'll is shown by sudden and strong
d. Election of the needle. 1t is exceed
ingly interesting 10 watch the grad
ual movement of the water, which can
be traced from the beginning Of the
experiment in this indirect way. By
this method the rate of flow ten feet
below the bed cf the Arkansas river
was found to be q feet per day.
Other experiments in the beds of the
Hondo and San Gabriel rivers in south
ern California, gave rates of 81? 4, 81
and I feet per day.
The knowledge of the underflow
that exists beneath the gravel of all
great valleys has been taken advan-
tage of in arid sections of the West,
where the running dry Of streams de-
prives irrigators of their water supply.
By excavating to bed rock in river
gravel and building an impervious
barrier across the channel, these un-
waters are saved in suffi-
cient quantities to be of great value to
the farmer. A notable subsurface dam
Of this kind has been constructed on
the Pacoima creek, California, to fur
nish water for irrigation and domestic
Deep Zones of f)w are a most i'm