The times., 1898-07-17
MODERN PRoJECTILEs.
Their Terrific Speed May Be Accu-
~ O. r0teIy measured.

II Is computed that the average velocity
of the larger guns on the cruiser New
York is 2,l00 feet per second. To the un-
initiated the way in which this Is found
out IL should be interesting.
In the first place it may be stated that
one cannot time projectile as one would
a horse. Some of them can be seen as
as they rush through the air. 1t is fav-
orite amusement during battery drill
with the old sea-coast guns at West
Point to stand behind and slightly OBJ
serve the gun. and watch the projectile
from the moment it leaves the muzzle
until it strikes the target planted on old
Gro Nest Mountain, about mile away.
Spectators with good eyesight can also see
the shell fired from the larger mortar
rise totthe highest point of its course. and
then descend with rush upon the noun
tain top, mile and half away, where
It bursts into many pieces.
lie Is reported that during the recent
bombardment of Santiago. the shells of
the cruiser New Orleans could be fol-
lowed by the eye. This was largely due
to the use OF smokeless powder, which
permit ted cfearsyision.
But in the case of smaller projectiles,
with greater velocity, ii is impossible to
see them during flight. But whether they
can be seen or not, it is quite out of the
question 10 time them as one would
race, by simply using the eye and stop
watch The least hesitation in pushing
the spring would make a difference of
hundreds of feet in the distance Travelled.
Errors such as these would make the re-
suits of no practical use.
Our small arm shoots bullet of only
one-third of an inch in diameter. which
travels two thousend feet in second, or
a mile in three. 1t goes so fast that 1t
becomes hot to the touch, due 10 the re-
sistence of the air which it pushes aside.
Strange to say the heated bullet will eau
terize the wound of its own making, and
few of the wounded in our war with
Spain will bleed TO death, unless struck
in vital spot.
The projectile has, beside forward We
Ioeity. a rotational velocity, which is
given to il by the rifing of the gun
Otherwise, since its length is much great
er than its diameter. il would soon be-
gin TO turn end on. The rifiing prevents
this by causing the bullet to bore path
through the air, and the higher the for
ward velocity the higher, too. must be the
rotational. This turning over ana over
would destroy the range and the accu-
racy of the gun.
The determination of the forward We
lOcity is now made with extreme accu-
racy The knowledge of ii is OF the ut
most Importance to military science. Va
rious methods have been adopted for its
determine tion within the gun. as Well
as at various points of the trajectory
The following method is the one adopted
by ali nations for finding the velocity OF
a proectile at any point of its path after
leaving the muzzle of the gun
The chrOnograph answers the purposes
Of a stop watch of greatest accuracy Two
bars are held up by electric magnets; the
currents flowing in one magnet also flows
through the second screen, while the cur
rent OF the other passes through the
second screen. The disjunctor Is an instru-
meat which Is used 10 break both circuits
at the same Instant. AS soon as this Is
done the bars fall, since the electr0-mag-
nets cease 10 Hct when there is no cur
rent flowing through them. The bar con-
nected with the first screen falls upon a
small platform. which releases wedge
shaped piece Of metal. This strikes the
bar connected with the second screen,
leaving a wedge shaped slit in il as a line
Of reference during the experiments.
This being done. the currents are estab-
lished again and the rods placed once
more under the influence Of the electro
magnets. Let a S.2-inch rife whose muz-
zle velocity is TO be found be placed in
front OF the first screen. The gun is
aimed fired. and its projectile passes
quicker than the roar of the discharge
through the first screen. breaking some
Of its wires in another instant il is
through the second screen. destroying its
electric current, and al last finds rest
ing place In some distant sand pile.
The break in each circuit is cOmmuni-
Gated to all parts of the line instantly
If the times at which both occur can be
determined, the problem is solved. For
instance, let the time it took 10 pass over
the fifty yards be .075 Of a second Then.
dividing the one by the other, gives 1903
feet per second as the velocity of the
prOjectile.
The time is found by accurately meas
uring the distance between the first dent,
the origin. and the second dent, caused
by the projectile breaking the circuits at
different times. To illustrate the princi-
pie involved: Ii the prOJectile be of low
velocity the distance will be greater than
if it travelled at a high rate of speed.
since the first rod would have longer
time 10 fall before the second starts. If
the distance be, say. one inch, then from
the law of falling bodies the time for that
can readily be found. and this will be the
time it took the projectile TO travel over
the fifty yards between the screens. Ex-
pressed mathematcally, this law is that
the time of fall is equal to twice the dis
tance of fall divided by gravity. Every
thing in this equation is known after the
experiment, excepting the time, which is
readily figured out.
So accurate Is this determination that
the velocity of the swiftest projectile can
be found to the fraction of foot. This
means the measurement of time to the
thousandth part of a second-a fraction
too small to comprehend.
The trajectory of projectile Is the path
it travels, and the way of discovering it
is simple. Screens are put up in line at
intervals of 100 yards. These are covered
with target cloth and are 50 built that
they can be raised or lowered by ropes
running over pulley9 which are in the
framework that supports the screens
The rife is put in wise, the muZZle be-
ing at the same height as the distant
bulTs-eye. Upon the discharge of the gun
the bullet will leave hole in each screen.
and from these its trajectory is easily de-
duced and transferred to paper.
This work is very important since a
bullet that rises over a mans head in
passing a distance of 500 yards is much
less effective than one which skins along
the ground for the same distance. For
instance in the comparison of the ira
jectories of modern small bore and the
| old Springfield. In going 500 yards the lat
| ter travels up SIG feet, while the former
only rises Ss5. BY examination of the
| chart it will also be seen that between 400
and 12e0 feet, or more than half the to-
! tai distance the bullet of the Springfield
passes above all ordinary-sized men.
| while that of the modern rifle would hit
! any man standing between the muzZle
and the bull's-eye 500 yards away. 1t is
| partly on account of these fiat trajecto-
ries that such terrible loss of life is ex-
pected in great war One or these bull
| lets will kill eight men and still have
| some energy TO spare.
| Guns of all sizes shoot much more rap
| idly than they did few years ago. This.
| cnr,, hinad with fat ira iect nries great Ve-