Essex County herald. [volume] (Guildhall, Vt.) 1873-1964, 1918-04-26

will have in pushing the projectile
from its course, either to the right or
left. These two corrections are
brought together and determine the
amount in degrees and minutes that
the muzzle of the gun must be shift
ed from the target to the right or
left in order that the projectile will
curve toward its goal At last we have
our gun controlled so that it will hit
the target.
larry just a moment. A gun, the
text books tell us, is the simplest form
of gas engine. Did you ever know
two gas engines of the same model
that acted alike? Neither will two
guns of the same model.
The Fifty Per Cent Zone.
If you have an automobile you know
| that the piston rings wear out, allow
! ing gases to escape, and thus reducing
the force with which the piston is
| forced down. Also the cylinder be-
Now, if you fire your gun many times
the same thing happens. The projec-
tile is the piston and the retaining
band of copper the piston ring that
seals the bore. If the bore is eroded
or If the rotating bands are not per
feet certain escape of gases occurs
and the fight of the projectle is con
sequently affected.
Again. there may be difference in
the weight of powder charges or in the
weight of the projectiles, which will
give slight variations in the flight OF
the proiectiles. SO that the battery
commander must know the dispersion
of each piece. This he finds out from
observation of his shots, and II
changes as the gun grows older. BY
figuring the deviation Of certain
group of proiectiles from the target
and which are known as trial shots OF
fire for adjustment, he finds out what
Is known as the mean error Of the
gun This, multiplied by the factor
S45. well known to students of prob
abilities, gives the mean probable er
rOr. Multiplying by two, the result ir
yards is what is known as the 80 pei
cent zone within which 80 per cent OF
his proiectiles. will fall. This compu
tatiOn is done longitudinally and lati
tudinally. giving certain OblOng strip
If the center of this strip can be
placed on the target by observation OF
fire the battery commander has done
Ian bot he nd
fire for effect. -Four times the sc
per cent zone gives the 100 per cent
zone, within which practically all his
shots will fall.
knowledge of these zones is all i'm
portant. BY this means he can figure
out how near he can come to our Owr
first line trenches without numbering
our infantry, and what is almost as
impOrtant, when it is necessary to save
ammunition he can easily compute how
many shots will be necessary to make
certain number Of hits on given
target.
And what about camouhage? The
enemy airplanes are on the alert and
all gun positions must he disguised
The battery commander must be q
master of camoutlage, able to erect
shelters and under their cover to build
his emplacements, while by the cXer'
else Of discipline ne restraints his men
from making tracks about the posi-
lions which will give away to the all
seeing eye Of the camera in the air
the fact that guns are mounted there
So that is why the student officers
Mt Fort Monroe blistered their
hands and strained their backs erect
ING camouflages and digging dugouts
and bombproofs; that is why they dove
and crawIed under motOrtrucks and
delved into differentials and gear
cases, emerging dirty and grimy, but
happy: that is why they toiled for
hours at night, working out lengthy
problems in trigonometry until angles
danced before their eyes when they
tried to sleep and endless chains OF
logarithms curved themselves through
their brain cells.