Cameron County press. [volume] (Emporium, Cameron County, Pa.) 1866-1922, 1910-07-21

- HE power of running water
ETTN TO remove sand, gravel
iSEhO and pebbles increases in
a remarkable degree with
HA the increase in velocity, so
a. that mining engineers can
Go make accurate calcula-
"A EAE tions concerning the ve-
EAAS locity which is necessary
10 remove stones of a certain size
IRON their sideways. The transport
ing power increases ca times with
each doubling of the velocity; so that
II you increase the velocity threefold
you have increased the transporting
power of the water 729 times and IL
you quadruple 1t you have increased
the weight Of the pebble which it
would move 1896 times. This at first
thought seems incredible, but it is
nevertheless true, and prepares us to
appreciate the astonishing results that
are produced by running water.
Water moving three feet in a sec
ond, or a mile in six hours, will carry
along with 1t particles OF fine clay
and keep them in suspension. Water
moving at twice that velocity will lift
and carry along with 1t fine sand;
while a velocity four times as great
will sweep along fine gravel and water
moving at the rate of two miles an
hour will carry along stones as big as
hens egg. There is hardly any limit
to the size of pebble that would be
rolled along by a current of six or
eight miles an hour, blocks as big as
houses being sometimes set in motion
and transported for considerable dis
tances.
In various ways one can obtain pos
tive evidence of this power Of water
transportation. If, for instance, he at
tempts to wade across the Platte
river in Nebraska, which is over
loaded with sand and has a gradient
of seven or eight feet to the mile, and
hence a very rapid current, he will
find his bare legs stung by the par
ticles OF sand and fine gravel that arei
driven against them. Or if after a
storm one pauses to listen he will
hear what sounds like distant can
nonading, produced by the knocking
of the stones together as they are
rolled along upon the bottom of the
stream.
The erosive power of a stream flow
ing over a rocky bed is determined by
its ability to shove along sand and
pebbles and gravel over its bottom. 1t
is these particles of solid matter that
accomplish the erosion, acting as a
rasp, or sandpaper, or more properly
a sand blast, to remove the solid rock
beneath and deepen the channel of a
stream. In order to do this, however.
there has to be proper adjustment be-
tween the supply of loose solid matter
to be transported and the volume and
velocity of the water. If there is more
sand and gravel than the current can
handle, this will accumulate upon the
bottom and Ill up rather than deepen
the bed. If there is too little material
the stream will flow over the rocks
without effecting much erosion, while
If there Is just the right amount OF
solid matter to be showed along Il will
deepen the channel with great rapid.
ity.
There are many striking examples
Of the work which has been accom-
plished by rivers in deepening and
their channels. We look
upon the rise OF mountain chains as
being most majestic Illustrations of
the power OF natural forces. but the
fact is equally impressive that I'm many
cases rivers which run across the line
Of mountain elevation are able to wear
down their channels as fast as the
mountains rise and thus maintain
their ancient onward course. The
Hudson river has thus sawed down a
channel through the solid rocks which
In ancient geologic times arose across
'ts course at West Point and below.
al that picturesque valley Of the Hud.
son being a valley Of erosion. The
Delaware river has worn an even
more striking gorge through the Blue
Ridge at the Delaware Water Can
where o. cuts directly across the very
hard strata at Medina sandstone con.
'tiiutlug Blue Ridge. forming perpen.
llcular walls on either side 900 feet
n height Similar eorges are found
.n the su#Gu.haHna and Potomac and
many other rivers along the Appa-
achian chain iust above where thew
merge upon tHe urroundlng Iowland.
We often speak uf such rivers AS
bursting through their barrier. BUT
here NIH UU HHr.fIur lH the 1rpra.