Volcano weekly ledger., 1855-11-24
For the Weekly Ledger.
Hydrodynamics.

draulics is Just now occupying good ueai Vi
attention amongst the miners, and exciting no
small amount of discussion, it is, perhaps, as
appropriate a subject for few remarks as
any other There is no place in the world
where hydrodynamics are so universally called
into action as in California, and if science can
aid the practical operator, to do so is certain
ly her province do not claim the ability
to treat the subject in learned manner, but
merely to give a few principles and facts in
hydraulics, which will be of service if noticed.
The power of water, as used for hydraulic
mining, does not depend on volume so much
as height. Supposing that the nozzle is one
inch in diameter, all the power that is obtain
ed is from column of water the heighth of
your hydraulic and of one inch diameter; all
the remaining water in your hose, is used only
to supply that column and keep it entirely
unbrokcn. A column of water, so feet high
and one inch diameter, will press with weight
of about 35l pounds upon its hose. 1t would
also press upon each square inch of the hose
that was at the same level, with the same
weight Now, unstop the hose, or nozzle,
and the pressure of 35I pounds to the inch
will still remain upon the hose but in this
event the water will escape with n veloc-
ity equal to the square root of the hcighth of
the column. Thus if with head Of one foot
an inch pipe will discharge 1922 inches per
minute, then with a height Of 81 feet the
same orifce will discharge 2449S inches with
velocity of 1920 feet per second. But
these laws of quantity and motion can only
be obtained where there is no friction or 9th
er opposing cause Under the most favora-
BILE circumstances one-twentieth must be de-
Quoted for friction, where the tubes are per
fectly smooth and straight, and here, where
the tubes are made of rough canvas and wind
ing and undulating along the ground like great
anacondas, it would be difficult to estimate
the amount of resistance with which the wa
ter meets. One matter of extreme import
ance in order to derive the full benefit of the
fall of water, is, to have the hose large. 1t
has been proven by experiment that n pipe
two inches in diameter and 100 feet long will
discharge five times as much water as one of
the same length one inch in diameter. The
section of a river ruus more rapidly when
stypl with tbot in 81 I.
cause of the greater quantity of water, but
because there is a larger portion of the water
not subjected to friction ON the bottom and
sides. In the centre of river also the cur
rent is swifter than ut the shores, for the rea-
son that there is no friction So in large
hose, the centre of the current will be less
obstructed by friction, or the reflex motion
produced by the windings of the hose
1t is mistaken idea to suppose that any
benefit is to be derived from large penstock.
All that is necessary is to have one large
enough to transmit to the hose the amount of
water it can convey. An orifce three inches
in diameter will deliver l33309 cubic inches
per minute, under head of 80 feet which is
222. lS feet per second, or as much as could
be delivered by long hose with total fall
OF 50 feet dcducting ordinary friction. To
supply this you would require a stream about
two and quarter inches deep twelve inches
wide, running at the rate of ten feet per sec.
ond, and the penstock some fifteen or eigh.
teen inches in diameter.
Great care should be taken to place the
hose as straight as practicable, as water is
governed by the same laws of motion as sol
ids whatever obstacle it meets retards its
motion, and the loss of velocity is proportions
ed to the obliquity of the detection.
1t has also been found that much depends
upon the kind of ori6ce through which water
is discharged Thus, in one tin vessel let there
be hole on inch in diameter in another a
tube one inch diameter, and three inches long
the latter will discharge 80 gallons while the
former discharges g. 1t is hence supposed
that the cross currents in the thin orifce. in
terfere with each other and prevent the water
dischargng so rapidly as in the tube. An
orihce twice the length of its diameter is
deemed the best.
The power of water then depends upon the
height OF the column above the discharging
oriice, and not upon its volume. The ouan-
tlty and velocity of discharge depend upon
The absence Of friction or detection, and upon