The Republican. [volume] (Oakland, Md.) 1877-current, 1880-02-07
Velocity Of a Rifle-Bullet.

account of lecture recently given bv
Prof. Robert Spice of the Cooper Insti-
tute, in which he accomplished the
task OF determining the actual velocity
OF rifie-bullet fired across the stage.
The distance measured on the platform
was thirty-three feet. To carry this
performance out he had secured the CO.
operation of Lieut.. E. L. Merriam, who
has gained some reputation at the
Creedmoor Range. In the first place,
Professor Spice called the attention of
the audience to mahogany base,
twelve inches by fifteen inches, on
which were placed two levers which
carried bent wires to make marks on q
piece of smoked glass underneath the
points. One of these wires was con-
nected with pendulum attached to an
Atwood machine, vibrating seconds.
BY means of electric currents the lever
connected with the pendulum came
down on the glass precisely at the be-
ginning of each second, making a
series of lines separated by spaces some
what similar to the old Morse alphabet.
Consequently the distance from the be-
ginning of one line to the beginning of
the next represented second of time.
The second lever, exactly opposite,
had spring attached to one end,
which kept the point off the glass. It
also had two electric magnets, one at
each end, which had electric currents
passed through of different strength
the weaker current tending to pull the
lever down on the glass, the stronger
current tending to keep it elevated. In
addition to this, the current from the
stronger magnet passed through loose
wire resting on two globules of mer-
wire was to rest the muzzle of the rifle.
The weaker current passed through
precisely similar loose wire, also on
two globules of mercury, which wire
was placed thirty-three feet distant
from the first wire.
Lieutenant Merriam now came for
ward and loaded his rifle. 1t was a
regular Creedmoor, 45-calibre, 34-inch
barrel, and placed in it a cartridge con-
tanning 450'grain ball and forty-fve
grains of powder; explaining that this
was not full charge. He then took
his position. The object was to shoot
away the wires on the mercury. A box
of sand was placed to receive the ball.
The pendulum above described was
then set in motion. On its striking the
fifth second the plate of smoked glass
was drawn along by the descent of
weight on the top of column of sand
which ran out of tube. On the sixth
second, Lieutenant Merriam pulled the
trigger and both wires vanished. On
the first wire being broken the point of
the corresponding lever descended on
the glass, but Immediately rose again
by the action of a spring, when the bull
let broke the second wire. The conse-
quence of this was that the point con-
nected with this lever scraped very
short line on the smoked glass;
while the other point, being kept down,
during the swing of the pendulum,
scraped longer space.
Then the glass was withdrawn and
placed in the stereopticon, projecting
magnified image of the lines on the
screen. The relative lengths of these
lines were ascertained, thus obviating
any source of error in measuring the
minute lines on the smoked glass. This
method of measuring the lengths was
claimed to be original by the Professor.
On this measurement it was found
that the shorter line was five inches
long, and the other line nine feet and
two inches. These numbers were
brought down to the common fraction
of inches, the result giving ITO inches
for the longer space. 1t was then as
certained how many times the former
L. la I'D In
fraction thus obtained was clearly the
fraction of second that the bullet took
to pass from one wire to the other
that is, 1922 of second. Multiplying
the distance between the wires (thirty-
three feet), as above, by the denomina-
tor of the above fraction, the velocity
of the bullet in feet was obtained, 726
feet in a second.