The weekly mountain Democrat. [volume] (Placerville, El Dorado County, Calif.) 1861-1862, 1862-10-25
The Way the Velocity Of Cannon
Balls IL Measured.


We recently had an opportunity of ex-
aiming the instrument in use at West
Point for measuring the velocity of can
non and musket shot, and we found it an
exceeding ingenious piece of mechanism.
In front ola graduated arc, two pendu-
lums are hung upon the same axle, one
little IN front Of the other, so that they
may swing pas each other. Each pendu.
lum carries a block Of iron near its lower
end by means of which it is held in hor-
iZUntal position by an electro magnet; one
pendulum being raised up on one side of
the arc, and the other upon the other
side. The cores of the electromagnetic are
made of the purest soft iron, so that when
the circuit of electricity which passes
along the wire around them is broken.
they will be instantly demagnetized, and
will consequently allow the pendnlums to
drop.
The wire from one electro magnet is
carried Ont Di ,snJys, n,l& A'>s'' :. ~ ~
across frame work target Just in front
OF the muzzlc OF the gun; and the wire
from the other magnet is drawn in the
same way across a target at 100 feet great
er distance. The gun is fired, and as the
shot passes through the targets it cuts the
wires Of both circuits, allowing the pen
dulums to fall But the wire near the
gun is cut sooner than the one more dis
tant. and, consequently, the pendulum
which is supported by Its magnet begins
to fall sooner 1L-2.. >Ar Sak}2e4~ tyt.odulum.
The pendulums therefore do not pass each
other az the iOwesS i0:7s( :; >hz S1'c, 6ut
at distance from the lowest point. Ehich
depends on the time occupied by the shot
in moving from one target to the other.
The exact point on the arc at which the
pendulumS pass each other is indicated
by little prick made in the arc as the
pendulums meet. 70 effect this the pen
dulum nearer the arc carries a pin point
ing toward the arc, the outer end Of the
pin having a beviled head which is hit by
a projection on the other pendulum as
the two meet, driving the point into the
arc.
The time occupied by the penduums in
making their oscillations is ascertained by
careful observations, and then the time
required for their passage through any
portion of their arc is known BY calcula-
ton. The instrument Is always nicely
adjusted Immediately before tits used, and
the experiments must be conducted with
the utmost thoroughne>> in every Respect.
When all the conditions are carefully COM
piled with, the velocity of shot is proba-
bly measured with more accuracy by this
instrument than by any other means yet
devised.
The idea of using electricity for deter
mining the velocity Of projectilcS was first
suggested by Wheatstone in 1910, and a
machine devised by Captain Navez, of the
belgian service, was tried in this country,
but was found too delicate and complica-
ted for general use, The machine which
we have described was designed by Capt.
j, &. Benton, late instructor of Ordnance
and Science of Gunncry, Military Acadc-
nay, West Point. 1t is crlled the electro
ba..iStic machine. - Scientific American.
Tnr FEDERAL TAx-I.iccn<cs for the
transaction of bu>ihc>S run for one year,
rt,I th.,, uin a,.t I,fl,u-