The Causes of Bad Shooting. Estimating Distances. Range-finding.
Rule for Sighting. General Duties of Artillery Commanders. Target
Practice. How Conducted. Projectiles Used. Kinds of Target.
Night-firing.
THE CAUSES OF BAD SHOOTING.
1. Variation in the density of loading.
2. Bad aiming.
3. Faults in handling ammunition, fuzes, etc.
4. Variable weights of charges and projectiles.
5. Inability to judge correctly the position of the bursts of the shell.
6. Failure to take into account the age and condition of the powder.
7. Variable wind.
=Variation in the Density of Loading.=--This is beyond the province of
the cannoneer, and need not, therefore, be considered.
=Bad Aiming.=--To obviate this, the men found to have the necessary
quickness of hand and eye should be utilized for this work, though all
should receive instruction in aiming. The sight should be carefully
examined before each shot, the same amount of the target should be
brought into the angle of the cross-wires, and a constant distance
between the eye and the rear sight should be maintained.
=Faults in Handling Ammunition, Fuzes, etc.; Variable Weights of
Cartridges and Projectiles; Failure to Take into Account the Age and
Condition of the Powder.=--Cartridges should be weighed, gauged,
and felt when received; otherwise there will be variations in range due
to more or less powder, to the make of the cartridge, or to caking.
If the cartridges of a battery vary much as to age, brand, etc. or if
they have travelled much, it would be well, when opportunity offers,
to break the lot up, mix the powder thoroughly, remake and reweigh
them. Be careful to use the copper measures and funnels, which can be
obtained from the Ordnance Department.
Time-fuzes are sometimes carelessly cut, or the safety-pin not removed.
=Inability to Judge Correctly the Position of Bursts of
Projectiles.=--The needful correction in elevation and fuzes cannot
be given unless it can be seen by the eye or glass, or by the aid of
observers, how the shells are bursting. While no provision has been yet
made therefor, a good telescope, with a tripod, and capable of being
moved by a micrometer screw, should be supplied to each battery in
service.
In making allowance for the wind move the sight into the wind; e.g., if
the projectile is carried too far to the right, on account of the wind
blowing from the left, move the sight _to the left_, and _vice versa_.
ESTIMATING DISTANCES.
The light, the state of the atmosphere, and the nature of the ground
are the chief disturbing causes in estimating distances and admit of no
rules.
The sun on one's back, a light background, water or snow to look over,
ground that is uniform and offers no prominent points of reference,
or when the air is particularly clear, as after a rain, tend to make
objects appear near.
A dark background, the sun in one's eyes, undulating ground to look
over, or when it is cut by ravines or covered by trees or dwellings,
or seen dimly at evening and in misty weather, tend to make objects
appear distant.
In estimating distance under the usual conditions:
Men's features can be distinguished at 300 yards, head-dress at 600
yards, movement of legs and arms at 1000 yards.
Infantry can readily be distinguished from cavalry at 1200 yards.
Individual men become vertical lines at 1500 yards.
Distinguishing between infantry and cavalry only by mode of motion at
1500 yards.
A mounted man looks like a speck or dot at 2000 yards.
One can perceive men and horses at 2200 yards.
One can count the windows of a house at 4300 yards.
By day the glittering of the sun upon the arms of troops in motion
indicates the direction of their march. If the rays are perpendicular,
they are moving directly toward you; if slanting from left to right
downwards, they are moving towards your right, and _vice versa_; if the
rays are intermittent and varied, they are moving away from you.
Dust raised by cavalry forms a high light cloud, by infantry a lower
and denser one, by wheeled vehicles denser still.
RANGE-FINDING.
The range is found by sound, by observation, by taking measurements
from the map, by means of range-finders, and by trial shots.
=By Sound.=--Multiply the number of seconds between burst of
projectile and report of same by 370 to obtain the approximate range in
yards.
=By Observation.=--As indicated in the rules given above regarding the
appearance of objects.
=By Taking Measurements from the Maps.=--This can be done on a good
topographical map on a large scale, taking care to fix thereon
accurately the position of the target and also the position of the gun.
=By Means of Range-finders.=--No range-finder has been adopted for our
service; but several instruments are now under consideration.
Whatever range-finder may be used, and with whatever care the range may
be taken, errors will exist; but they may be reduced to a minimum by a
good instrument and skilled observers.
=Trial Shots.=--If the range be doubtful or unknown, trial shots will
be used, but it must be remembered that trial shots disclose your
position.
Estimate the range, give the elevation indicated for it by the range
table, and the necessary drift (or deflection), each unit of the
deflection scale on the sight corresponding to 1/345[8] of the range,
and proceed as indicated under Target Practice, page 379.
=Sighting.=--The nearer the eye is to the rear sight the better will
the front sight be seen, and the finer can the sight be taken. The same
distance should be taken for each shot, if possible. In setting the
sight it is well to bear in mind that the deviation of the projectile
follows the motion of the rear-sight point: thus, if it be moved up
further than is required, the projectile will strike high; if it be
moved too far to the right, the projectile will go too far to the right
of the object aimed at. Also in allowing for the wind move the sight
_into the wind_, i.e, in the direction the wind comes from.
GENERAL DUTIES OF ARTILLERY COMMANDERS.
THE CHIEF OF ARTILLERY.
The chief of artillery to the general commanding issues the orders for
the distribution and concentration of fire, according to the phases
of the battle and the plans of the general. As a rule, the method of
carrying out these orders, the projectile used, the rapidity and order
of fire, will be left to the commanders of groups of batteries.
THE CHIEF OF CORPS ARTILLERY.
The officer commanding the corps artillery designates the target for
each of his battalions, and controls the fire of the corps artillery in
accordance with the instructions he receives.
THE BATTALION COMMANDER.
=Fire Control.=--The commander of an artillery battalion prescribes the
method to be used for finding the range, designates the target for each
battery, and prescribes the projectile to be used, the rate and order
of fire, and the concentration or distribution of fire on the targets
in range. His orders and directions that cannot be given by voice or
trumpet are conveyed by his staff or non-commissioned staff.
THE BATTERY COMMANDER.
=Regulation of Fire.=--This includes control over all the details of
the service of the guns, the corrections in observation, deflection,
the length of fuze, and the concentration and distribution of fire
within the limits of a designated target that are necessary in order to
obtain the most effective fire upon it.
The captain regulates the fire of his battery, and, if acting
independently, he also controls it. He remains mounted or dismounted
at pleasure, and places himself, as a rule, near one of the flanks
and sufficiently close to the battery that his orders may be readily
understood. The corrections for lateral deviations are generally
intrusted to the chiefs of platoons.
Finding the range by the method designated, and the regulation of
the fire according to the target, range, projectile, and observed
effect, are intrusted to the captains of batteries, and it is only in
exceptional cases that the battalion commander takes personal command
in order to find the range or to regulate the fire.
Artillery fire is effective in proportion to its concentration. The
long range of the guns permits a concentration of their fire on many
different points without change of position. When practicable, the
groups that are intended to fire on the same target should be placed
under the control of one officer. In the advance-guard action the
artillery of the assailant covers, and the artillery of the defence
opposes, the deployment and advance of the advance-guard infantry.
In the preliminary stages of a battle and the commencement of the
artillery duel the fire is usually directed on the targets immediately
opposite the batteries engaged; as soon as portions of the enemy's
artillery-line are subdued the fire is concentrated on the different
targets in succession, taking them in the order of their relative
importance; during the preparation and delivery of the assault the fire
of the assailants is concentrated against the point of attack; the fire
of the defence is concentrated against the attacking infantry as soon
as it shows itself.
Fire should be directed against batteries that are changing positions,
and in order that this brief opportunity of inflicting serious damage
may not be lost a part of the batteries of the defence should be
especially instructed to open fire on hostile batteries while limbering
or in movement without waiting for orders.
The defence generally offers more favorable opportunities for
long-range fire than the offence, but whether advantage is to be taken
of these opportunities must be determined by the general commanding,
who will have to decide whether the effect of the fire will compensate
for the partial or complete disclosure of the position that it
involves. Ordinarily artillery should avoid opening fire at a greater
range than 3000 yards. Beyond this distance it is difficult to observe
the effect of fire even with good glasses. Longer range fire is used
in exceptional cases against objects that are clearly seen and are
of considerable extent, such as villages, camps, or large bodies of
troops. Ineffective cannonades at long distances, and shelling woods
or other localities not positively known to be occupied by the enemy,
should not be permitted. The position from which fire is first opened
may necessarily be much less than 3000 yards, in order to obtain view
of the enemy.
Firing over friendly troops should be avoided as much as possible.
Batteries that support an assault from a distance continue their fire
upon the point of attack until it becomes dangerous to the assailants;
they then either increase the range considerably in order to cover the
ground beyond, or they direct their fire on other points of the enemy's
line. Artillery does not fire at long ranges from positions in rear
during a pursuit, on account of the danger to the pursuing troops; in
such cases it should advance rapidly and endeavor to establish itself
on the flanks of the enemy's line of retreat, where it will find the
most advantageous positions.
As a general rule, the fire of artillery is directed against that arm
of the enemy which at the time is predominant, or which is capable
of inflicting the greatest loss on the infantry or cavalry that the
artillery is supporting. During the artillery duel the artillery
generally avoids firing at the other arms; but if large bodies of
infantry or cavalry appear in open ground within effective range a
portion of the guns should be directed upon them.
TARGET PRACTICE.
The artillery that first finds the range will have a great advantage in
the artillery duel, and in all cases its correct establishment is the
first condition of accurate shooting.
=Observation of Fire.=--Correct observation of the effects of fire
is necessary in order to make the required corrections, and is
indispensable to good shooting. It can only be acquired by much
practice under the varying conditions of the wind, light, state of
the atmosphere, background, foreground, and nature of the target, and
is rendered more difficult in action by smoke and the liability of
mistakes when more than one battery is firing at the same target. For
medium as well as long ranges a good field-glass is required.
As a rule, the observation is limited to ascertaining whether the
shots are short or over. The observation of direct hits is unreliable
except at very short ranges, or when palpable effects are produced in
the enemy's ranks, limbers are blown up, or there are other manifest
indications of the effect produced. When a target is on a height or
behind a parapet, it is possible to distinguish hits on the slope
of the hill or on the parapet, and to estimate correctly the error
in range of the projectiles that fall short. There are no means of
estimating the error in range of the projectiles that fall beyond the
target, except when a battery is on an elevation and firing at a target
on a plane below it; here shots striking beyond the target may be
observed and the error estimated.
When several batteries are firing at the same target, and it is
difficult to distinguish the individual rounds, a fire by battery will
give a group of shots that may be recognized.
The observation of the fire will be facilitated by the reports of an
officer or non-commissioned officer stationed some distance in advance
and outside one of the flanks of the guns.
=Smoke.=--When the wind is across the range and blows the smoke in
front of the guns, it will be difficult to correctly aim and properly
observe the effects of the fire. In the case of a single battalion
this inconvenience may be diminished by increasing the interval
between the batteries, or may be avoided by advancing the batteries
in echelon from the leeward flank so that the smoke of each windward
battery will drift behind those to the leeward of it. This last measure
has the disadvantage of making the leeward batteries conspicuous
against the white background of smoke, and besides is not always
practicable, especially when the position is on the brow of a hill.
If neither of the above expedients can be adopted, and it is not
possible to sufficiently increase the interval of time between the
guns in each battery to permit the smoke to blow away, the fire by
battery or platoon may be used, or the battalion commander may order
the battalion to fire by piece, commencing on the leeward flank. When
several battalions are together, as large intervals as possible should
be left between them, or, if the ground permits, the battalions should
be advanced in echelon from the leeward flank, in order to diminish or
avoid the inconvenience of smoke drifting across the range.
When the target cannot be seen on account of smoke which hangs in front
of the guns, or on account of fog, rain, or darkness, the pieces may be
aimed by means of auxiliary targets.
=Finding the Range.=--This is the work of the battery commander. He
and the range party precede the battery to the position, and as soon
as the exact position of his battery is indicated by the battalion
commander he observes carefully the position of the target, its nature
and extent, and estimates the range by means of a map, any source
available, or range-finder (all if possible), very carefully, and
especially so when the fire is to be over the heads of other troops.
He estimates the ranges to other points within the field of fire which
might subsequently become targets, and observes:
Nature and position of any covering mass.
Zones of ground which ought to be cannonaded.
Nature of soil in vicinity of target, if possible.
Exact part of target on which to aim his guns in determining the range.
If the range be determined only by observation, it will be necessary to
use trial shots.
In finding the range by trial shots it is of great importance that the
object and the particular part of it to be fired at should be clearly
understood. In order to avoid mistakes the captain may direct one of
the officers or non-commissioned officers to rectify the aim of all
the guns after they have been pointed. Care should be taken that all
the guns are aimed at exactly the same point; that the exact elevation
ordered by the battery commander is used, and not changed until ordered
by him; and that the result of every shot is carefully observed.
The range can be more accurately and quickly found when each battery
has a different target and one directly in front of it to fire at. If
the target is a long line, it should be divided into as many sections
as there are batteries to fire at it, and each captain should select
a gun or object in the part assigned him. In such case the battalion
commander can compare the elevations obtained by the several batteries,
and if they agree, and the observation of the fire indicates good
results, it is fair to assume that the range is correct. When several
batteries are to open a long-range fire on a small target, the
battalion commander generally designates the battery, and preferably
that on the leeward flank, to find the range. Batteries that come into
action at short distances from the enemy's line generally find the
range by firing salvos at a prominent point of the target.
As a rule, percussion-shell are used to find the range, and all the
guns of a battery are aimed at one point of the target; if shrapnel
with percussion-fuze be used, the same principles apply.
In firing at intrenchments, however, the fire may be distributed from
the first, even for obtaining the range, as the hits, as a rule, can be
easily observed.
The enemy's flanks are designated, and the guns in his batteries are
numbered, as he himself would designate or number them.
The firing to obtain the range should be slow and deliberate, and ample
time afforded to observe each shot and make the necessary corrections.
When a battery unlimbers near another battery already in action and
opens fire upon the same target, it should obtain the range from the
latter.
The duty of finding the range generally devolves upon the captain of
each battery, even when several batteries open fire upon the same
target. Whenever several batteries open simultaneously to find the
range of a target of limited dimensions, the fire of each battery
must be concentrated upon an entirely distinct point, and all of the
points must be far enough apart to enable each battery commander
to distinguish the fall of his own projectiles from those of the
neighboring battery.
It is only in very exceptional circumstances that the battalion
commander would take personal charge of the firing of his battalion in
order to establish the range himself.
=Trial Shots.=--A percussion-shell is fired with the elevation
corresponding to the estimated range at a clearly visible and sharply
defined fixed point of the target.
If the first shot strikes short, or beyond the target, the range for
the second is either increased or decreased, according to the case, so
as to throw the shot beyond or short of the target.
These corrections are generally made as follows:
When firing at short ranges, 100 yards.
" " " medium " 200 "
" " " long " 400 "
Such firing is pursued until two consecutive shots fall, one short of
and the other beyond the target, which establishes "the long bracket,
or fork."
No round should be taken as a basis for correction if there is any
doubt as to the reliability of the observations.
A mean range is taken from those two which determined the long fork
for the next shot, and then another shot is fired at a range obtained
by taking the mean of the last range and the one of the long fork
whose shot fell on the opposite side of the target. So proceed until
the target is enclosed between two consecutive shots only 50 yards
apart. This is called "the short fork, or bracket." Then a verifying
group, generally a shot from each gun is fired with the elevation
corresponding to the mean range of the short fork. If four out of six
of the shots fall short, the range is established; and if shrapnel-fire
is then resorted to the range is still further reduced by 50 yards.
When the range has been measured, and not estimated, the short fork may
be obtained from the first two shots.
If the elevation has not been obtained as above indicated, at known
ranges shrapnel-fire may commence, as if the range had already been
determined by shell-fire; at unknown ranges the trial-shot firing with
shrapnel is conducted as with shell; that is to say, the elevation is
increased or reduced from shot to shot (by 100 yards at short range,
200 yards at medium range) until the target is enclosed between at
least two accurately observed shots, one over and the other short.
The difference is reduced as already described until the mean of
the short fork is obtained. The large fork should be established by
percussion-shrapnel, and then fire time-shrapnel.
During the ranging platoon commanders indicate exactly the point to
aim at, see that the sights are properly set, especially during the
first rounds, observe similarly the time-fuze, and make any necessary
correction for deflection; which deflection pertains to a particular
gun, and is not carried to another. Bear in mind that each unit of the
scale for deflection corresponds to 1/345 of the range for sights now
used.[9]
After the ranging has been completed, if a gun makes a constant error,
the platoon commander may be permitted to change the elevation ± 25
yards.
The general rule for vertical and lateral corrections is: when the
deviation exceeds the amount of mean dispersion, a correction should
be made after one round; but if it is equal to or less than this
several rounds are fired with the same elevation or deflection, and a
correction made according to their mean deviation.
The battery commander indicates the length of fuze for time-shrapnel.
If firing at artillery and all the guns are equally conspicuous, the
fire should be directed upon one of the central guns, otherwise at the
most conspicuous gun; if the wind is blowing across the range, the fire
should be directed upon the most conspicuous gun on the windward flank.
If firing upon masses of troops, the fire should be directed upon the
centre of the first line; if firing upon skirmishers, it should be
directed first upon one point, then another, close in front of the line.
PROJECTILES TO BE USED.
=Percussion-shell.=--For ranging, against material, and in default of
shrapnel against living targets.
Against troops behind loopholed walls,--if it explodes after passing
through, use percussion-shrapnel,--stockades, abattis, barricades,
entanglements, etc.
Direct hits are necessary when it is used against guns, limbers,
earthworks, obstacles, etc., and its effects are then due
to percussion, penetration, and the explosive force of the
bursting-charge. When used against men or horses, it is burst on first
graze close in front of the target, and its effects are then produced
by its splinters. The smoke made by the large bursting-charge of the
percussion-shell aids the observation of fire.
The effect of projectiles with percussion-fuzes is dependent on the
nature of the ground in front of the target; soft marshy ground,
hollows, and cuts diminish its effect, while hard smooth ground
increases it.
Percussion-shell gives the best results when the fire is concentrated.
It can sometimes be advantageously distributed, provided that several
guns keep a part of the target under superior fire.
=Shrapnel with Time-fuze= is used against all living targets, provided
they be not close behind cover, troops behind slight cover, such as
shelter-trenches, banks, etc., gun-pits and epaulments, balloons,
batteries limbered up or in action, ammunition and other trains, unless
firing particularly against the material. With the fuze set at zero it
can be used for close defence in default of canister.
The effect of shrapnel is due to the penetration of its bullets and
splinters; this penetration is small, and it is therefore employed
against men and horses only. It has a combination fuze and can be made
to burst either in the air or on the first graze, and can therefore be
made independent of the nature of the ground in front of the target.
Made to burst high by means of its time-fuze, it can be used against
living targets behind cover, against which percussion-shell could have
but little effect.
Burst the projectiles 50 yards short and about 6 yards (at medium
ranges) above, the object aimed at. A rough rule for height of burst
is height of burst in _feet_=the number of hundred yards in range.
In firing at troops behind cover, such as banks, rising ground, or
earthworks, burst the projectiles about 25 yards, or less, in front
of, and from 7 to 10 feet above, the cover.
=Shrapnel with Percussion-fuze= is generally used against moving
targets, for rapid firing, and for firing over friendly troops; against
enemy's troops in a village or woods; metal shields; and in cavalry
combats as soon as the ground which was masked by one's own troops
becomes cleared.
Shrapnel gives the best results when the fire is distributed, a part of
the target being apportioned to each gun. When the time-fuze is used,
it will often be advisable to vary the elevation and length of fuze in
each battery so as to cover about 200 yards in depth, and thus bring
the enemy's supports and reserves, as well as his front line, under
fire.
=Canister= is used against living targets at close ranges. Its effect
is largely diminished when the ground in front of the guns is rough or
soft, and particularly when covered with brush or standing crops. It
would be used against cavalry at 500 yards, and against infantry at 300
yards.
=Order of Fire.=--The order of fire is habitually by piece in each
battery, and usually commences on the leeward flank. It is the most
effective, as the errors in the service of any one gun can generally be
observed, and therefore corrected.
Salvos, or the fire by battery, may be used to find the range under
circumstances that render it difficult to observe a single shot, to
avoid the inconvenience of smoke, and occasionally, instead of rapid
fire by piece, to take advantage of quickly passing opportunities.
The fire at will is only used in the defence of the guns at very short
ranges.
The fire by piece from one flank of a battalion to the other may be
used to avoid smoke, or to enable the field-officer commanding the
battalion to take personal charge of the firing in order to find
the range under difficult circumstances, or to regulate the fire in
exceptional cases.
The fire by platoon is only used to facilitate the observation of fire
under exceptional circumstances that permit two shots to be observed
more easily than one, and also to increase the interval of time between
successive discharges, to allow the smoke to drift away, without
diminishing the amount of fire. In most cases the fire by piece or by
battery is preferable to it.
=Rapidity of Fire.=--The rapidity of fire is dependent on the range,
the circumstances of the action, the facilities for the observation of
the fire, and the amount of unexpended ammunition.
=Slow Fire= is used at long ranges and for obtaining the range, and
generally in the commencement of the action and during the artillery
duel; it is also used in prolonged actions, and when the ammunition is
running short. The interval between successive shots should not be less
than 30 seconds, and may be slower.
=Ordinary Fire= is used when the fire is effective, but when the
circumstances of the action do not demand a rapid fire. It is at the
rate of 1 shot every 20 seconds, or, in a six-gun battery, 6 rounds in
2 minutes.
=Rapid Fire.=--The rate is about one round in 7 seconds; it should be
sufficient to enable the effect of a shot to be observed before firing
the next one.
_The range being accurately known_, it is used: when the enemy's
batteries are coming into action; when there is a very favorable
target; when a rush is made to pass a defile; when covering the advance
of one's own artillery; when the decisive infantry attack is about to
take place; when the advance is checked during a critical situation;
when the opportunity to fire is very fleeting; at short ranges.
The instant the necessity for rapid fire ceases to exist the fire
should revert to the ordinary rate.
TARGETS MOVING TOWARDS THE BATTERY.
The range is found by trial shots, the elevation being increased or
reduced by stages of 100 or 200 yards, depending on circumstances.
As soon as a shell is observed to fall not too short (within 100 yards
of the advancing target) all the guns fire a round rapidly.
If infantry is being fired at, each subsequent round should have its
range diminished by 100 yards; if cavalry or artillery, at a trot or
gallop, it should be diminished 200 and 300 yards respectively.
TARGETS MOVING FROM THE BATTERY.
Two elevations differing by 100 yards are obtained as before; with the
lower of the two a salvo of shrapnel is fired from all the guns in the
battery, the proceeding is then repeated, and so on.
TARGETS MOVING OBLIQUELY AND ACROSS THE FRONT OF THE BATTERY.
If the target is of great length, aim at the head of it; if not of
great length or moving rapidly, aim in front of it.
Under certain circumstances it is advisable to ascertain the range
of points in the line of march of the target. When the moving target
reaches one of these points, fire rapidly. Infantry cover 1½ yards a
second at a quick walk, and artillery and cavalry 2 yards a second at a
quick walk, 4 yards at a trot, and 6 yards at a gallop. By multiplying
the rate per second of the target by the time of flight of a shell, we
obtain the distance the target has moved over during the flight of the
shell.
INDIRECT FIRING.
In firing at an object which cannot be seen from the gun several
methods are employed, depending on the circumstances of the case.
1st. Plant a picket for each gun on the crest of the ridge whence the
object to be fired at can be seen; behind the ridge line a second
picket with the first picket and the object, run the guns up to any
convenient distance in rear of the pickets, and get them in line with
each pair of pickets; the deflection-scale can be used to remedy any
small lateral errors. The elevation is given by means of a gunner's
quadrant or pointing-arc if available. If not, set a stake in front
of the line of wheels and in rear of the muzzle, and immediately in
the plane of sight, its height equal to the vertical distance from the
top of the trunnion-sight to the ground; (for 3.2-inch gun 3′ 10″.68;
for 3.6-inch gun 3′ 11″.16). Then give the rear sight the elevation
corresponding to the range and aim at this point, using peep-and
cross-hairs. An observer is necessary, and by means of his reports the
necessary corrections are given until the elevation and length of fuze
have been determined. After each shot care must be taken to run the gun
up to the position it occupied before firing.
2d. =In Firing at Troops in Ravines and Hollows= when they cannot be
seen from the battery select a stone or bush, or any distinguishable
object, on the side of the ravine or hollow as an auxiliary target,
and obtain the elevation and fuze for it; then by means of the lateral
deviation of the sight change the direction of fire, and elevation and
fuze if necessary. In such a case an observer on the flank or some
commanding position is absolutely necessary.
3d. =By Means of a Compass.=--Select a distant auxiliary mark that
can be seen from the gun; from a position as near the gun as possible
obtain the angle between the auxiliary mark and the object; construct
this angle at the gun and mark the position of the wheels; give
elevation as previously explained, and make corrections by reports
from an observer. The Germans have a device for measuring this angle:
it consists practically of a horizontal graduated arc bearing an arm
containing two vertical sights. It is placed on the gun, set at the
angle indicated by the compass, and the gunner sights at the auxiliary
object.
NIGHT-FIRING.
For night firing, or when there is much fog, a luminous aiming-point
is required. This may be readily obtained by the use of a bull's-eye
lantern. Soften the light by placing paper or other material over the
glass, and draw thereon two right lines intersecting at right angles
at the centre of the glass. At a convenient distance in front of the
gun and in the plane of fire place the lantern on a post so that the
point of intersection of the lines shall be at such a height that when
the rear sight is at zero, _and the axis of the gun horizontal_, it
can be directly aimed at. Establish a plumb-line between the lantern
and the gun so that the plumb-line, the point of intersection of the
lines on the lantern, and the object aimed at are in the same vertical
plane. (The above requirements must of course be completed during the
day, when the object can be seen.) Give the rear sight the elevation
corresponding to the range, and aim at the point where the plumb-line
covers the point of intersection of the two lines on the glass of the
lantern.
If a gunner's quadrant or pointing-arc be available, simply determine
and mark accurately the direction for each piece, and give elevation by
either instrument.