Full Text Archive logoFull Text Archive — Free Classic E-books

Aeroplanes and Dirigibles of War by Frederick A. Talbot

Part 3 out of 4

Adobe PDF icon
Download this document as a .pdf
File size: 0.4 MB
What's this? light bulb idea Many people prefer to read off-line or to print out text and read from the real printed page. Others want to carry documents around with them on their mobile phones and read while they are on the move. We have created .pdf files of all out documents to accommodate all these groups of people. We recommend that you download .pdfs onto your mobile phone when it is connected to a WiFi connection for reading off-line.

victor has come to earth, subsequent examination has revealed the
enormous strains to which the aeroplane has been subjected. The
machine has been distorted; wires have been broken--wires which
have succumbed to the enormous stresses which have been imposed
and have not been snapped by rifle fire. One well-known British
airman, who was formerly a daring automobilist, confided to me
that a fight in the air "is the finest reliability trial for an
aeroplane that was ever devised!"

In these desperate struggles for aerial supremacy the one party
endeavours to bring his opponent well within the point-blank
range of his armament: the other on his part strives just as
valiantly to keep well out of reach. The latter knows fully well
that his opponent is at a serious disadvantage when beyond
point-blank range, for the simple reason that in sighting the
rifle or automatic pistol, it is difficult, if not impossible
while aloft, to judge distances accurately, and to make the
correct allowances for windage.

If, however, the dominating aviator is armed with a machine gun
he occupies the superior position, because he can pour a steady
hail of lead upon his enemy. The employment of such a weapon
when the contest is being waged over friendly territory has many
drawbacks. Damage is likely to be infficted among innocent
observers on the earth below; the airman is likely to bombard his
friends. For this very reason promiscuous firing, in the hope
of a lucky shot finding a billet in the hostile machine, is not
practised. Both parties appear to reserve their fire until they
have drawn within what may be described as fighting distance,
otherwise point blank range, which may be anything up to 300
yards.

Some of the battles between the German and the French or British
aeroplanes have been waged with a total disregard of the
consequences. Both realise that one or the other must perish,
and each is equally determined to triumph. It is doubtful
whether the animosity between the opposing forces is manifested
anywhere so acutely as in the air. In some instances the combat
has commenced at 300 feet or so above the earth, and has been
fought so desperately, the machines climbing and endeavouring to
outmanoeuvre each other, that an altitude of over 5,000 feet has
been attained before they have come to close grips.

The French aviator is nimble, and impetuous: the German aviator
is daring, but slow in thought: the British airman is a master of
strategy, quick in thought, and prepared to risk anything to
achieve his end. The German airman is sent aloft to reconnoitre
the enemy and to communicate his information to his headquarters.
That is his assigned duty and he performs it mechanically,
declining to fight, as the welfare of his colleagues below is
considered to be of more vital importance than his personal
superiority in an aerial contest. But if he is cornered he
fights with a terrible and fatalistic desperation.

The bravery of the German airmen is appreciated by the Allies.
The French flying-man, with his traditional love for individual
combat, seeks and keenly enjoys a duel. The British airman
regards such a contest as a mere incident in the round of
duty, but willingly accepts the challenge when it is offered. It
is this manifestation of what may be described as acquiescence in
any development that enabled the British flying corps, although
numerically inferior, to gain its mastery of the air so
unostentatiously and yet so completely.

All things considered an aeroplane duel is regarded as a fairly
equal combat. But what of a duel between an aeroplane and a
dirigible? Which holds the advantage? This question has not
been settled, at any rate conclusively, but it is generally
conceded that up to a certain point the dirigible is superior.
It certainly offers a huge and attractive target, but rifle fire
at its prominent gas-bag is not going to cause much havoc. The
punctures of the envelope may represent so many vents through
which the gas within may effect a gradual escape, but
considerable time must elapse before the effect of such a
bombardment becomes pronounced in its result, unless the gas-bag
is absolutely riddled with machine gun-fire, when descent must be
accelerated.

On the other hand, it is to be presumed that the dirigible is
armed. In this event it has a distinct advantage. It has a
steady gun-platform enabling the weapons of offence to be trained
more easily and an enhanced accuracy of,fire to be obtained. In
order to achieve success it is practically imperative that an
aeroplane should obtain a position above the dirigible, but the
latter can ascend in a much shorter space of time, because its
ascent is vertical, whereas the aeroplane must describe a spiral
in climbing. Under these circumstances it is relatively easy for
the airship to outmanoeuvre the aeroplane in the vertical plane,
and to hold the dominating position.

But even should the aeroplane obtain the upper position it is not
regarded with fear. Some of the latest Zeppelins have a machine
gun mounted upon the upper surface of the envelope, which can
be trained through 360 degrees and elevated to about 80 degrees
vertical. Owing to the steady gun platform offered it holds
command in gun-fire, so that the aeroplane, unless the aviator is
exceptionally daring, will not venture within the range of
the dirigible. It is stated, however, that this upper gun has
proved unsatisfactory, owing to the stresses and strains imposed
upon the framework of the envelope of the Zeppelin during firing,
and it has apparently been abandoned. The position, however, is
still available for a sniper or sharpshooter.

The position in the sky between two such combatants is closely
analogous to that of a torpedo boat and a Dreadnought. The
latter, so long as it can keep the former at arm's, or rather
gun's, distance is perfectly safe. The torpedo boat can only
aspire to harass its enemy by buzzing around, hoping that a lucky
opportunity will develop to enable it to rush in and to launch
its torpedo. It is the same with the aeroplane when arrayed
against a Zeppelin. It is the mosquito craft of the air.

How then can a heavier-than-air machine triumph over the unwieldy
lighter-than-air antagonist? Two solutions are available. If it
can get above the dirigible the adroplane may bring about the
dirigible's destruction by the successful launch of a bomb. The
detonation of the latter would fire the hydrogen within the
gas-bag or bags, in which event the airship would fall to earth a
tangled wreck. Even if the airship were inflated with a
non-inflammable gas--the Germans claim that their Zeppelins now
are so inflated--the damage wrought by the bomb would be so
severe as to destroy the airship's buoyancy, and it would be
forced to the ground.

The alternative is very much more desperate. It involves ramming
the dirigible. This is undoubtedly possible owing to the speed
and facile control of the aeroplane, but whether the operation
would be successful remains to be proved. The aeroplane would be
faced with such a concentrated hostile fire as to menace its own
existence--its forward rush would be frustrated by the dirigible
just as a naval vessel parries the ramming tactics of an enemy by
sinking the latter before she reaches her target, while if it did
crash into the hull of the dirigible, tearing it to shreds,
firing its gas, or destroying its equilibrium, both protagonists
would perish in the fatal dive to earth. For this reason ramming
in mid-air is not likely to be essayed except when the situation
is desperate.

What happens when two aeroplanes meet in dire combat in mid-air
and one is vanquished? Does the unfortunate vessel drop to earth
like a stone, or does it descend steadily and reach the ground
uninjured? So far as actual experience has proved, either one of
the foregoing contingencies may happen. In one such duel the
German aeroplane was observed to start suddenly upon a vol-plane
to the ground. Its descending flight carried it beyond the lines
of the Allies into the territory of its friends. Both came to
the conclusion that the aviator had effected his escape. But
subsequent investigation revealed the fact that a lucky bullet
from the Allies' aeroplane had lodged in the brain of the German
pilot, killing him instantly. At the moment when Death over took
him the aviator had set his plane for the descent to the ground,
and the machine came to earth in the manner of a glider.

But in other instances the descent has been far more tragic. The
aeroplane, deprived of its motive power, has taken the deadly
headlong dive to earth. It has struck the ground with terrific
violence, burying its nose in the soil, showing incidentally that
a flying machine is an indifferent plough, and has shattered
itself, the debris soaked with the escaping fuel becoming
ignited. In any event, after such a fall the machine is certain
to be a wreck. The motor may escape damage, in which event it
is salvaged, the machine subsequently being purposely sacrificed
to the flames, thereby rendering it no longer available to the
enemy even if captured. In many instances the hostile fire has
smashed some of the stays and wires, causing the aeroplane to
lose its equilibrium, and sending it to earth in the manner of
the proverbial stone, the aviators either being dashed to pieces
or burned to death.

What are the vulnerable parts of the aeroplane? While the
deliberate intention of either combatant is to put his antagonist
hors de combat, the disablement of the machine may be achieved
without necessarily killing or even seriously wounding the
hostile airman. The prevailing type of aeroplane is highly
susceptible to derangement: it is like a ship without armour
plate protection. The objective of the antagonist is the motor
or the fuel-tank, the vital parts of the machine, as much as the
aviator seated within.

A well-planted shot, which upsets the mechanism of the engine, or
a missile which perforates the fuel tank, thereby depriving the
motor of its sustenance, will ensure victory as conclusively as
the death of the aviator himself. Rifle fire can achieve either
of these ends with little difficulty. Apart from these two
nerve-centres, bombardment is not likely to effect the desired
disablement, inasmuch as it cannot be rendered completely
effective. The wings may be riddled like a sieve, but the
equilibrium of the machine is not seriously imperilled thereby.
Even many of the stays may be shot away, but bearing in mind the
slender objective they offer, their destruction is likely to be
due more to luck than judgment. On the other hand, the motor and
fuel tank of the conventional machine offer attractive targets:
both may be put out of action readily, and the disablement of the
motive power of an enemy's craft, be it torpedo-boat, battleship,
or aeroplane, immediately places the same at the assailant's
mercy.

Nevertheless, of course, the disablement of the airman brings
about the desired end very effectively. It deprives the driving
force of its controlling hand; The aeroplane becomes like a ship
without a rudder: a vessel whose helmsman has been shot down. It
is unmanageable, and likely to become the sport of the element in
which it moves. It is for this reason that aviators have been
urged to direct their fire upon the men and mechanism of a
dirigible in the effort to put it out of action. An uncontrolled
airship is more likely to meet with its doom than an aeroplane.
The latter will inevitably glide to earth, possibly damaging
itself seriously in the process, as events in the war have
demonstrated, but a helpless airship at once becomes the sport of
the wind, and anyone who has assisted, like myself, in the
descent of a vessel charged with gas and floating in the air, can
appreciate the difficulties experienced in landing. An
uncontrolled Zeppelin, for instance, would inevitably pile up in
a tangled twisted ruin if forced to descend in the manner of an
ordinary balloon. Consequently the pilot of a dirigible realises
to the full the imperative urgency of keeping beyond the
point-blank fire of aerial mosquito craft.

The assiduity with which British aviators are prepared to swarm
to the attack has been responsible for a display of commendable
ingenuity on the part of the German airman. Nature has provided
some of its creatures, such as the octopus, for instance, with
the ways and means of baffling its pursuers. It emits dense
clouds of inky fluid when disturbed, and is able to effect its
escape under cover of this screen.

The German aviator has emulated the octopus. He carries not only
explosive bombs but smoke balls as well. When he is pursued and
he finds himself in danger of being overtaken, the Teuton aviator
ignites these missiles and throws them overboard. The aeroplane
becomes enveloped in a cloud of thick impenetrable smoke. It is
useless to fire haphazard at the cloud, inasmuch as it does not
necessarily cover the aviator. He probably has dashed out of the
cloud in such a way as to put the screen between himself and his
pursuer.

In such tactics he has merely profited by a method which is
practised freely upon the water. The torpedo boat flotilla when
in danger of being overwhelmed by superior forces will throw off
copious clouds of smoke. Under this cover it is able to steal
away, trusting to the speed of the craft to carry them well
beyond gunshot. The "smoke screen," as it is called, is an
accepted and extensively practised ruse in naval strategy, and is
now adopted by its mosquito colleagues of the air.

CHAPTER XIII
TRICKS AND RUSES TO BAFFLE THE AIRMAN

The airman has not been allowed to hold his undisputed sway in
military operations for long. Desperate situations demand
drastic remedies and already considerable and illuminating
ingenuity is being displayed to baffle and mislead the scout of
the skies.

It is a somewhat curious and noteworthy fact, that the Germans
were among the first to realise the scope of the airman's
activities, and the significance of their relation to the
conveyance of intimate information and the direction of artillery
fire. Consequently, they now spare no effort to convey illusory
information, in the hope that the hostile force may ultimately
make a false move which may culminate in disaster.

Thus, for instance, as much endeavour is bestowed upon the
fashioning of dummy trenches as upon the preparation of the
actual lines of defence. And every care will be taken to
indicate that the former are strongly held. The dug-outs are
complete and at places are apparently cunningly masked. If the
airman is flying swiftly, he is likely to fail to distinguish the
dummy from the real trenches. To him the defences appear to be
far more elaborate and more strongly held than is the actual
case.

The advantage of this delusion is obvious when a retreat is being
made. It enables the enemy to withdraw his forces deliberately
and in perfect order, and to assume another and stronger position
comparatively at leisure. The difficulty of detecting the
dummies is emphasised, inasmuch as now, whenever the sound of an
aeroplane is heard, or a glimpse thereof is obtained, the men
keep well down and out of sight. Not a sign of movement is
observable. For all the airman may know to the contrary, the
trenches may be completely empty, whereas, as a matter of fact,
they are throbbing with alert infantry, anxious for a struggle
with the enemy.

This is one instance where the dirigible is superior to the
aeroplane. The latter can only keep circling round and round
over the suspicious position; the movement through the air
interferes with close continuous observation. On the other hand,
the dirigible can maintain a stationary position aloft for hours
on end. Then the issue is resolved into a contest of patience,
with the advantage to the airman. The soldiers in the trenches
fret and fume under cover; confined concealment is irksome and is
a supreme test of the nerves. Unless the soldiers are made of
very stern stuff, physical endurance succumbs. Some rash act--
apparently very trivial--may be committed; it suffices for the
vigilant sentinel overhead. He detects the slender sign of life,
forms his own conclusions, and returns to his headquarters with
the intelligence that the enemy is playing "Brer Rabbit."

It has also become increasingly difficult for the airman to
gather absolutely trustworthy data concerning the disposition and
movement of troops. Small columns are now strung out along the
highways to convey the impression that the moving troops are in
far greater force than is actually the case, while the main body
is under the cover offered by a friendly wood and is safe from
detection. The rapidity with which thousands of men are able
to disappear when the word "Airman" is passed round is
astonishing. They vanish as completely and suddenly as if
swallowed by the earth or dissolved into thin air. They conceal
themselves under bushes,in ditches, lie prone under hedgerows,
dart into houses and outbuildings--in short, take every cover
which is available, no matter how slender it may seem, with
baffling alacrity. The attenuated column, however, is kept
moving along the highway for the express purpose of deceiving the
airman.

Advancing troops also are now urged to move forward under the
shelter of trees, even if the task entails marching in single or
double file, to escape the prying eyes of the man above. By
keeping close to the line of trunks, thus taking full advantage
of the overhanging branches, and marching in such a manner as to
create little dust, it is possible to escape the aerial scout.

The concealment of cavalry, however, is somewhat difficult. An
animal, especially if he be unaccustomed to the noise of the
aeroplane, is likely to become startled, and to give vent to a
frightened and vociferous neighing which invariably provokes a
hearty response from his equine comrades. The sharp ear of the
airman does not fail to distinguish this sound above the music of
his motor. Again, he has come to regard all copses and stretches
of undergrowth with suspicion. Such may or may not harbour the
enemy, but there is no risk in making an investigation. He
swoops down, and when a short distance above the apparently
innocent copse, circles round it two or three times. Still
undecided, he finally hurls a bomb. Its detonation invariably
proves effective. The horses stampede and the secret is out.
Even foot soldiers must be severely trained and experienced to
resist the natural inclination to break cover when such a missile
is hurled into their midst.

Frequently a force, which has laboured under the impression that
it is safe from detection, has revealed its presence unwittingly
and upon the spur of the moment. If the men be steeled against
the bomb attack, it is almost impossible to resist the
inclination to take a shot when the airman, swooping down,
ventures so temptingly near as to render him an enticing target
almost impossible to miss. As a rule, however, the observer is
on the alert for such a betrayal of a force's existence. When
the bomb fails to scatter the enemy, or the men are proof against
the temptation to fire a volley, a few rounds from the
aeroplane's machine gun often proves effective. If the copse
indeed be empty no harm is done, beyond the abortive expenditure
of a few rounds of ammunition: if it be occupied, the fruits of
the manoeuvre are attractive. Cunning is matched against
cunning, and the struggle for supremacy in the art of craftiness
is keen.

The French Flying Corps have had recourse to an ingenious ruse
for accomplishing two ends--the one to draw concealed artillery
fire, and the other to pre-occupy the airmen. Two German aerial
scouts observed a French machine flying at a somewhat venturesome
height over their masked artillery. Divining the reason for the
hostile intrepidity they gave chase. Circling round the French
machine they assailed it with machine-gun fire. The enemy
appeared to take no notice but continued his gradual descent in a
steady line.

Presently the German airmen, having drawn sufficiently near,
observed that the French aviator was inert. Had he been killed?
Everything pointed to such a conclusion, especially as they had
raked the aeroplane fore and aft with bullets. But still
suspicious they continued their circling movements, their
attention so concentrated upon their quarry that they had not
observed another move. It was the crash of guns from their
masked artillery which broke in upon their absorption. Looking
round, they observed three French aeroplanes soaring around and
above them at high speed. Scarcely had they realised the
situation before a spirited mitraireuse fire was rained upon
them. One of the German aeroplanes was speedily disabled. Its
fuel tank was riddled and it sank rapidly, finally crashing to
earth in the deadly dive head foremost, and killing both its
occupants in the fall. The second aeroplane hurried away with
its pilot wounded. In the excitement of the aerial melee the
first French aeroplane had been forgotten. It was now scarcely
100 feet above the German artillery. A capture appeared to be
imminent, but the Germans received a rude surprise. Suddenly the
aeroplane exploded and a hail of shrapnel burst over the heads of
the artillerymen.

The circumstance was decidedly uncanny, but after two or three
such experiences of exploding aeroplanes the matter was
explained. The apparently helpless aeroplane was merely a
glider, which, instead of carrying a man, had a booby-trap
aboard.

It appears that the French airmen have found a use for the
aeroplanes which are considered unsafe for further use. The
motor and propeller are removed and the dummy of explosives is
strapped into position. The laden glider is then taken aloft by
means of an airship, and in the concealment of the clouds is
released, the rudder being so set as to ensure a gradual
vol-plane towards the suspicious position below. The explosive
cargo is set with a time fuse, the arrangement being that the
contents will be detonated while the machine is near the ground,
unless this end is accelerated by a well-planted shell from an
anti-aircraft gun. The decoy glider is generally accompanied by
one or two aeroplanes under control, which keep under the cover
of the clouds until the hostile aviators have been drawn into the
air, when they swoop down to the attack. The raiders are fully
aware that they are not likely to become the target of fire from
the ground, owing to the fact that the enemy's artillery might
hit its friends. Consequently the antagonistic airmen are left
to settle their own account. In the meantime the dummy machine
draws nearer to the ground to explode and to scatter its
death-dealing fragments of steel, iron, and bullets in all
directions.

Possibly in no other phase of warfare is subterfuge practised so
extensively as in the concealment of guns. The branches of trees
constitute the most complete protection and guns are placed in
position beneath a liberal cover of this character. The branches
also offer a screen for the artillerymen, who can lurk beneath
this shelter until the aeroplane has passed. To complete the
illusion dummy guns fashioned from tree trunks and the wheels of
useless limbers are rigged up, and partially hidden under
branches, the idea being to convey the impression to the man
aloft that they are the actual artillery.

The aerial scout observes the dummies beneath the sparse covering
of branches. Congratulating himself upon his sharp eyesight, he
returns to his base with the intelligence that he has found the
enemy's guns he indicates their position upon the map, and in
some cases returns to notify the position of the weapons by
smoke-ball or tinsel, when they are immediately subjected to a
severe bombardment. He follows the shell-fire and sees the arms
put out of action. He returns to camp satisfied with his
exploit, oblivious of the smiles and laughter of the hostile
artillerymen, who have their guns safely in position and well
masked some distance away. The dummies are imperfectly concealed
purposely, so that they may be discovered by the aerial scout,
while the real guns are completely masked and ready to belch
forth from another point. In one or two cases the dummies have
been rigged up in such a manner as to convey the impression, when
seen from aloft, that a whole battery has been put out of action,
barrels and wheels as well as broken limbers strewing the ground
in all directions.

Moving masses of soldiers are also resorting to cunning in order
to mislead the airman or to escape his observation. At the
battle of Haelen, during which engagement the German warplanes
were exceptionally active, the Belgian soldiers covered their
heads with bundles of wheat snatched from the standing stooks,
and under this cover lurked in a field where the corn was still
standing. From aloft their forms defied detection: the
improvised headgear completely covered them and blended
effectively with the surrounding wheat. In another instance the
French misled a German airman somewhat effectively. What
appeared to be cavalry was seen to be retreating along the
country road, and the airman returned hurriedly to report. A
German squadron was dispatched in hasty pursuit. But as it
rounded a copse skirting the road it received a murderous fire at
close quarters, which decimated the ranks and sent the survivors
flying for their lives along the road up which they had ridden so
confidently. Had the aviator been in a position to observe the
horses more closely, he would have found that what appeared to be
riders on their backs were in reality sacks stuffed with straw,
dressed in old uniforms, and that a mere handful of men were
driving the animals forward. The cavalrymen had purposely
dismounted and secreted themselves in the wood in anticipation of
such a pursuit as was made.

While the Germans do not appear to be so enterprising in this
form of ingenuity they have not been idle. A French airman
flying over the Teuton lines observed the outermost trenches to
be alive with men whose helmets were distinctly visible. The
airman reported his observations and the trench was subjected to
terrific shell fire. Subsequently the French made a spirited
charge, but to their dismay found that the outermost German
trench was occupied by dummies fashioned from all sorts of
materials and crowned with helmets! This ruse had enabled the
German lines to be withdrawn to another position in safety and
comparatively at leisure.

Before war was declared the German military experts were
emphasising the importance of trees for masking troops and guns
against aerial observation. One of the foremost authorities upon
military aviation only a few months ago urged the German Military
Staff to encourage the planting of orchards, not for the purpose
of benefiting agriculture or in the interests of the farmers, but
merely for military exigencies.

He pointed to the extensive orchards which exist in
Alsace-Lorraine and Baden, the military covering value of which
he had determined from personal experience, having conducted
aerial operations while military were moving to and fro under the
cover of the trees. He declared that the cover was efficient and
that under the circumstances the laying out of extensive orchards
in strategical places should be carried out without any delay.
This, he urged, was a national and not a private obligation. He
advocated the bestowal of subsidies on the farmers to encourage
the planting of fruit trees. He suggested that the trees should
be provided by the State, and given to all who were prepared to
plant them; that substantial prizes should be awarded to
encourage the rapid growth thereof, and that annual prizes should
be awarded to the man who would undertake their cultivation and
pruning, not from the fruit-yielding point of view, but for
facilitating the movement of troops beneath their dense branches.

He even urged the military acquisition of suitable land and its
determined, skilful, and discreet exploitation by those who loved
the Fatherland. He emphasised the necessity for keeping such
orchards under military control, only vouchsafing sufficient
powers to the local authorities to ensure the desired
consummation. He maintained that, if the work were prosecuted
upon the right lines and sufficient financial assistance were
given, the purpose in view could be achieved without saddling the
war department with any unremunerative or excessive burden. He
admitted that the process of raising fruit trees to the stage
when they would afford adequate cover would be tedious and
somewhat prolonged, but argued that the military advantages, such
as enabling troops to move below the welcome shelter with
absolute freedom and without physical fatigue, would be an ample
compensation.

The utility of such cover to artillery was another factor he did
not fail to emphasise. He dwelt seriously upon the difficulty of
rendering permanent gun emplacements and heavy artillery
invisible to the airman by resort to the usual type of gun
shields. The latter may be located with ease by alert airmen,
whereas if the guns were under cover of fruit trees they would be
able to accomplish their deadly mission without betraying their
presence to the aerial scout. Moreover, by pruning the trees in
such a manner as to ensure free movement beneath, the artillery
would be able to advance without betraying the fact to the enemy.

This authority vigorously insisted that the work should be
carried out without a moment's delay as it was vital to the
Fatherland. In the light of recent events, and the excellent
cover which is offered by the orchards of the territory he cited
as an illustration of his contention, such a disclosure is
pregnant with meaning. It throws a new light upon the thorough
methods with which the Germans carried out their military
preparations, and incidentally shows that they were fully alive
to every possible development. Fruit-raising as a complement to
military operations may be a new line of discussion, but it
serves to reveal the German in his true light, ready for every
contingency, and shows how thoroughly he appreciates the danger
from the man in the clouds.

CHAPTER XIV
ANTI-AIRCRAFT GUNS. MOBILE WEAPONS.

When the airship and the aeroplane became accepted units of
warfare it was only natural that efforts should be concentrated
upon the evolution of ways and means to compass their destruction
or, at least, to restrict their field of activity. But aircraft
appeared to have an immense advantage in combat. They possess
virtually unlimited space in which to manoeuvre, and are able to
select the elevation from which to hurl their missiles of
destruction.

There is another and even more important factor in their favour.
A projectile fired, or even dropped, from a height, say of 5,000
feet, is favourably affected by the force of gravity, with the
result that it travels towards the earth with accumulating energy
and strikes the ground with decisive force.

On the other hand, a missile discharged into space from a weapon
on the earth has to combat this action of gravity, which
exercises a powerful nullifying influence upon its flight and
velocity, far in excess of the mere resistance offered by the
air. In other words, whereas the projectile launched from
aloft has the downward pull of the earth or gravitational force
in its favour, the shell fired from the ground in the reverse
direction has to contend against this downward pull and its
decelerating effect.

At the time when aircraft entered the realms of warfare very
little was known concerning the altitudes to which projectiles
could be hurled deliberately. Certain conclusive information
upon this point was available in connection with heavy howitzer
fire, based on calculations of the respective angles at which the
projectile rose into the air and fell to the ground, and of the
time the missile took to complete its flight from the gun to the
objective. But howitzer fire against aircraft was a sheer
impossibility: it was like using a six-inch gun to kill a fly on
a window pane at a thousand yards' range. Some years ago certain
experiments in aerial firing with a rifle were undertaken in
Switzerland. The weapon was set vertically muzzle upwards and
discharged. From the time which elapsed between the issue of the
bullet from the muzzle until it struck the earth it was possible
to make certain deductions, from which it was estimated that the
bullet reached an altitude of 600 feet or so. But this was
merely conjecture.

Consequently when artillerists entered upon the study of fighting
air-craft with small arms and light guns, they were compelled to
struggle in the dark to a very pronounced extent, and this
darkness was never satisfactorily dispelled until the present
war, for the simple reason that there were no means of getting
conclusive information. The German armament manufacturers
endeavoured to solve the problem by using smoking shells or
missiles fitted with what are known as tracers. By following the
ascensional path of the projectiles as revealed by the smoke it
was possible to draw certain conclusions. But these were by no
means convincing or illuminating, as so many factors affected the
issue.

Despite the peculiar and complex difficulties associated with the
problem it was attacked some what boldly. In this trying field
of artillery research the prominent German armament
manufacturers, Krupp of Essen and Ehrhardt of Dusseldorf, played
a leading part, the result being that before the airship or the
aeroplane was received within the military fold, the
anti-aircraft gun had been brought into the field of applied
science. The sudden levelling-up serves to illustrate the
enterprise of the Germans in this respect as well as their
perspicacity in connection with the military value of aircraft.

Any gun we can hope to employ against aircraft with some degree
of success must fulfil special conditions, for it has to deal
with a difficult and elusive foe. Both the lighter-than-air and
the heavier than-air craft possess distinctive features and
varying degrees of mobility. Taking the first-named, the
facility with which it can vary its altitude is a disconcerting
factor, and is perplexing to the most skilful gunner, inasmuch as
he is called upon to judge and change the range suddenly.

On the other hand, the artilleryman is favoured in certain
directions. The range of utility of the airship is severely
limited. If its avowed mission is reconnaissance and conclusive
information concerning the disposition of forces, artillery and
so forth is required, experience has proved that such work cannot
be carried out satisfactorily or with any degree of accuracy at a
height exceeding 5,000 feet, and a distance beyond six miles.
But even under these circumstances the climatic conditions must
be extremely favourable. If the elements are unpropitious the
airship must venture nearer to its objective. These data were
not difficult to collect, inasmuch as they were more or less
available from the results of military observations with captive
balloons, the conditions being somewhat similar. With the
ordinary captive balloon it has been found that, in clear
weather, a radius of about 3 3/4 miles at the maximum elevation
constitutes its range of reliable utility.

With the aeroplane, however, the conditions are very dissimilar.
In the first place the machine owing to its diminutive size as
compared with the airship, offers a small and inconspicuous
target. Then there is its high independent speed, which is far
beyond that of the airship. Furthermore its mobility is greater.
It can wheel, turn sharply to the right or to the left, and
pursue an irregular undulating flight in the horizontal plane,
which renders it well nigh impossible for a gunner to pick it up.
The machine moves at a higher relative speed than that at which
the gun can be trained. It is the rapid and devious variation
which so baffles the gunner, who unless he be highly skilled and
patient, is apt to commence to fire wildly after striving for a
few moments, and in vain, to pick up the range; he trusts to luck
or depends upon blind-shooting, which invariably results in a
waste of ammunition.

A gun, to be of tangible destructive efficiency when directed
against aircraft, especially those depending upon the gas-bag for
equilibrium, must be of special design. It must be capable of
firing at an angle only a few degrees less than the absolute
vertical, and in order to follow the rapid and involved movements
of its objective, must be so mobile that it can be trained
through a complete circle at any angle of inclination less than
its maximum. At the same time, if the weapon is being used in
field operations it must be mounted upon a carriage of adequate
mobility to enable it to follow the airship, and thereby keep
pace with the latter, so that the aerial craft may be sorely
harassed if not actually hit. The automobile is the obvious
vehicle for this duty, and it has accordingly been extensively
used in this service.

The automobile and the gun mounted thereon follow widely
different lines. Some vehicles are designed especially for this
duty, while others are improvisations, and be it noted, in
passing, that many of the latter have proved more serviceable
than the former. Still, the first-named is to be preferred,
inasmuch as necessarily it is designed to meet the all-round
requirements imposed, and consequently is better able to stand up
to the intended work, whereas the extemporised vehicle is only
serviceable under favourable conditions.

The Krupp Company has evolved many designs of anti-aircraft
motor-driven guns--"Archibalds" the British airmen term them with
emphatic levity. They are sturdily-built vehicles fitted with
heavy motors, developing from 40 to 50 horse-power, with the
chassis not widely dissimilar from that adopted for motor-omnibus
traffic. Consequently, they are not necessarily condemned to the
high-roads, but within certain limits are able to travel across
country, i.e., upon fields or other level expanses, where the
soil is not unduly soft.

But the very character of the problem rendered the evolution of
the vehicle a somewhat perplexing matter. There were many
factors which had to be taken into consideration, and it was
possible to meet the imposed requirements only within certain
limits. In the first place, the weight of the gun itself had to
be kept down. It was obviously useless to overload the chassis.
Again, the weight of the projectile and its velocity had to be
borne in mind. A high velocity was imperative. Accordingly, an
initial velocity varying from 2,200 to 2,700 feet per second,
according to the calibre of the gun, was determined.

Moreover, as mobility was an indispensable condition, the gun had
to be so mounted that it could be fired from the motor-car even
if the latter were travelling at high speed. This requirement
entailed another difficulty. The gun had to be mounted in such a
manner as to enable the gunner to train it easily and readily
through the complete circle and through its complete range of
vertical inclination. As the result of prolonged experiments it
was ascertained that the most suitable arrangement was a pedestal
mounting, either within a turret or upon an open deck. To meet
the weight of the gun, as well as the strains and stresses
incidental to firing, the chassis was strengthened, especially
over the rear axle near which the mounting is placed.

The heaviest gun of this type is the 10.5 centimetre (4 1/4-inch)
quick-firer, throwing a shell weighing nearly forty pounds, with
an initial velocity of 2,333 feet per second. This "Archibald"
is totally unprotected. The gun is mounted centrally upon the
carriage over the rear axle, and occupies the centre of the deck
between the driver's seat and that of the gun crew behind. The
whole of the deck is clear, thereby offering no obstruction to
the gunner in training the weapon, while the space may be widened
by dropping down the wings of the vehicle. At the rear is a seat
to accommodate the gun crew, beneath which the ammunition is
stowed. When travelling and out of action, the gun lies
horizontally, the muzzle pointing from the rear of the car.

To reduce the strains arising from firing, the arm is fitted with
what is known as the "differential recoil." Above the breach is
an air recuperator and a piston, while there is no hydraulic
brake such as is generally used. The compressor is kept under
compression while the car is travelling with the gun out of
action, so that the arm is available for instant firing. This is
a departure from the general practice in connection with such
weapons. When the gun is loaded the bolt which holds the
compressor back is withdrawn, either by the hand for manual
firing, or by the action of the automatic closing of the
breech when the arm is being used as a quick-firer. In firing
the gun is thrown forward under the pressure of the released air
which occurs at the moment of discharge. The energy of the
recoil brings the gun back and at the same time recharges the
compressed air reservoir.

The gun is so mounted upon its pedestal as to enable a maximum
vertical inclination of 75 degrees to be obtained. The mounting
system also enables the weapon to be trained in any desired
direction up to the foregoing maximum elevation throughout a
complete circle, and it can be handled with ease and celerity. A
smaller "Archibald" is the 7.5 centimetre (3-inch gun) throwing a
14.3 pound shell at an initial velocity of about 2,170 feet per
second.

The turret anti-aircraft gun carried upon a motor-car differs
from the foregoing very considerably. This is a protected arm.
The gun of 7.1 centimetres--approximately 2.75 inches--is mounted
in the same manner upon the car-deck and over the driving axle,
but is enclosed within a sheet steel turret, which is proof
against rifle and machine-gun fire. This turret resembles the
conning-tower of a battleship, and is sufficiently spacious to
house the whole of the gun crew, the internal diameter being
about seven feet. Access to the turret is obtained through a
rear door. This gun has a maximum elevation of about 75 degrees,
while its operation and mechanism are similar to those of the
unprotected weapon.

The vehicle itself is practically identical with the armoured
motor-car, which has played such an important part during the
present campaign, the driver being protected by a bullet-proof
steel screen similar in design to the ordinary glass wind-screen
fitted to touring automobiles. This is carried sufficiently high
to offer complete protection to his head when seated at the
wheel, while through a small orifice in this shield he is able to
obtain a clear view of the road. The engine and its vital parts
are also adequately protected. The ammunition is carried in a
cupboard-like recess forming part of the driver's seat, encased
in bullet-proof steel sheeting with flap-doors. This device
enables the shells to be withdrawn readily from the side of the
car and passed to the crew within the turret. The caisson is of
sufficient dimensions to receive 69 shells.

The Ehrhardt airship fighting ordnance is similarly adapted to
motor-car operations, one type being especially powerful. The
whole of the vehicle is encased in armour-plating impervious to
rifle and machine-gun fire. The driver is provided with a small
orifice through which he is able to obtain a clear uninterrupted
view of the road ahead, while the armouring over the tonneau is
carried to a sufficient height to allow head-room to the gun crew
when standing at the gun. All four wheels are of the disk type
and fashioned from heavy sheet steel. The motor develops 40-50
horse-power and, in one type, in order to mitigate the risk of
breakdown or disablement, all four wheels are driven. The gun, a
small quick-firer, is mounted on a pedestalin a projecting
conning-tower. The mounting is placed behind the driver's seat,
and is trained and operated from the tonneau. The maximum
elevation is 75 degrees, and like the gun carriage bearing the
tube guide it can be moved through a complete circle, being free
to rotate in the fixed pivot jack to enable this end to be
attained.

The foregoing may be said to represent the most powerful types of
mobile anti-aircraft weapons used by the Austro-German forces
to-day. Arms of similar design, roughly speaking, have also been
introduced into the French and Russian services. In addition
many semi-armoured weapons of this character are in operation,
some specially built for the work, while others have been
improvised. In the semi-armoured motor-car the carriage follows
the usual lines; it has an open top, the armouring comprising the
body of the tonneau and the diskwheels, which are made of light
bullet-proof steel. Here again the prevailing practice is to
mount the gun as nearly above the rear axle as possible, and
to work it from the tonneau. The maximum elevation is also 75
degrees, with training throughout the entire circle.

Another type comprises a very light machine gun of rifle calibre,
and this is intended for attachment to an ordinary motor car.
There is a pedestal mounting which can be set within the tonneau,
while the weapon is pivoted in an outrigger, the latter being
free to rotate in its pivot jack. This arrangement enables the
arm to cover a wide range,while it also admits of training
through an extensive angle of elevation.

The Allied forces improvised travelling anti-aircraft offences
by mounting the latest types of Vickers, Hotchkiss, and other
machine guns in armoured motor cars. Some of these have the
domed turret form, with the gun projecting through the roof,
while others are protected against hostile attack from the side
only, the carriage being panelled with bullet-proof steel
sheeting. While such weapons are useful, inasmuch as they can
maintain a hot fire ranging up to 750 shots per minute, they are
not to be compared with the "Archibalds," which are able to throw
heavy shrapnel and incendiary shells, and have a vertical range
of about 6,000 to 8,000 feet.

The improvised motor-gun has not proved a complete success,
except in those instances when the hostile aircraft has ventured
to approach somewhat closely to the ground. The more formidable
weapons cannot be mounted upon ordinary vehicles, inasmuch as the
increase in weight, which is appreciable, impairs the efficiency
of the vehicle, and at the same time enhances the possibility of
breakdown at a critical moment. For such arms a special and
substantial chassis is imperative, while the motive power and
gearing must be adapted to the circumstances.

Motor-mounted anti-aircraft weapons, however, have not proved an
unqualified success. The fact that the vehicles are condemned to
the high roads, or at least to comparatively smooth and level
ground, constitutes a severe handicap. Again, when travelling at
high speed, and this is essential when pursuing a fast aeroplane,
the accurate laying of the weapon is extremely difficult, owing
to the oscillation of the vehicle itself, especially if the road
surface is in a bad condition. The sighting arrangements are of
a wonderfully complete character, as described elsewhere, but the
irregular rolling movement arising from high speed is a
nullifying quantity. It is tolerably easy for the aircraft,
especially an aeroplane, to evade successful pursuit, either by
rising to an elevation beyond the range of the gun, or by
carrying out baffling evolutions such as irregular undulating
flight, wheeling, and climbing. According to the reports of the
British and French airmen the "Archibald" has failed to establish
the glowing reputation which was anticipated, for the simple
reason that, unless it has a clear straight road and can maintain
its high speed, it can easily be out-distanced by the fleet human
bird.

The motor-car suffers from another serious disability. It cannot
manoeuvre with sufficient celerity. For instance, if it is
necessary to turn round in a narrow lane, valuable time is lost
in the process, and this the airman turns to account. In hilly
country it is at a still greater disadvantage, the inclines,
gradients, and sinuosities of the roads restricting its
effectiveness very pronouncedly. It must also be remembered
that, relatively speaking, the "Archibald" offers a better target
to the airman than the aeroplane offers to the man behind the
anti-aircraft gun on the motor below. A few well-placed bombs
are sufficient to induce the pursuers to cease their activities.
Even if the missiles fail to strike the motor-car itself they can
wreak disaster in directly by rendering the road impassable or
dangerous to negotiate at high speed. On the whole therefore,
the "Archibald" is a greatly exaggerated weapon of offence
against aircraft, and, so far as is known, has failed to fulfil
expectations. In fact, the Germans have practically abandoned
the idea of using it in the manner of a pursuing arm; they work
the weapon as a fixture, depending upon the car merely as a means
of moving it from point to point. Thus, in reality, it has been
converted into a light field-piece, and may almost be included in
the category of fixed weapons for combating aerial operations.

CHAPTER XV
ANTI-AIRCRAFT GUNS. IMMOBILE WEAPONS

The immobile anti-aircraft gun, as distinct from that attached to
a travelling carriage such as a motor-car, may be subdivided into
two classes. The one is the fixed arm which cannot be moved
readily, mounted upon a permanent emplacement; the other is the
field-piece which, while fired from a stationary position, may be
moved from point to point upon a suitable carriage. The
distinction has its parallel in ordinary artillery, the
first-named weapon coinciding with the heavy siege gun, which is
built into and forms part and parcel of the defensive or
offensive scheme, while the second is analogous to the field
artillery, which may be wheeled from position to position.

In this phase of artillery the Germans led the way, for the
simple reason that they recognised the military value of aerial
navigation years in advance of their contemporaries. Again, in
this field the Krupp Organisation has played a prominent part.
It embarked upon actual construction of weapons while its rivals
in other countries were content to prepare their drawings, which
were filed against "The Day." But it must not be thought that
because the German manufacturers of armaments were ahead of
their contemporaries they dominated the situation. Far from it.
Their competitors in the market of destruction were every whit as
keen, as ingenious, and as enterprising. Kruppism saw a
commercial opportunity to profit from advertisement and seized
it: its rivals were content to work in secret upon paper, to keep
pace with the trend of thought, and to perfect their
organisations so as to be ready for the crisis when it developed.

The first Krupp anti-aircraft field-piece was a 6.5 centimetre (2
9/16 inch) arm. It possessed many interesting features, the most
salient of which was the design of the axle of the carriage. The
rigid axle for the two wheels was replaced by an axle made in two
sections, and joined together in the form of a universal
coupling, so that each wheel virtually possessed its own axle, or
rather half-axle. This was connected with the cradle of the gun
in such a manner that the wheels were laterally pivoted thereon.

The result is that each axle can be turned forward together with
its wheel, and thus the wheels have their rims brought into line
to form an arc of a circle, of which the rear end of the spade of
the gun carriage constitutes the centre. This acts as a pivot,
about which the gun can be turned, the pair of wheels forming the
runners for the achievement of this movement. The setting of the
weapon in the firing position or its reversion to the travelling
position can be easily and speedily effected merely by the
rotation of a handwheel and gearing.

With this gun a maximum elevation of 60 degrees is possible,
owing to the trunnions being carried well behind the breech in
combination with the system of long steady recoil. The balancing
spring which encloses the elevating screw is contained in a
protected box. The recoil brake, together with the spring
recuperator, follows the usual Krupp practice in connection with
ordinary field pieces, as does also the automatic breech-closing
and firing mechanism. In fact there is no pronounced deviation
from theprevailing Krupp system, and only such modifications as
are necessary to adapt the arm to its special duty. When the gun
is elevated to high angles the shell, after insertioin the
breech, is prevented from slipping out by means of a special
device, so that the proper and automatic closing of the breech is
not impaired in any way.

In such an arm as this, which is designed essentially for
high-angle firing, the sighting and training facilities require
to be carried out upon special lines, inasmuch as the objective
is necessarily at a considerable altitude above the horizon of
the gun. In other words, in firing at a high inclination,
distance between the gun and the target cannot be utilised
directly for the back sight. On the other hand, it is essential
that in proportion as the angle from the horizontal increases,
the back sight should be lowered progressively in a manner
corresponding to the distance.

To assist the range-finder in his task of sighting it is
necessary that he should be provided with firing tables set out
in a convenient form, which, in conjunction with the telemeter,
serve to facilitate training for each successive round. In this
way it is possible to pick up the range quickly and to keep the
objective in the line of fire until it either has been put hors
de combat, or has succeeded in retiring beyond the range of the
gun.

The sighting arrangements of these Krupp anti-aircraft guns are
carried out upon these lines. Beneath the barrel of the
back-sight is an observing glass with an eye-piece for the
artillerist, while above and behind the observing glass is
another eye-piece, to be used in conjunction with the
manipulation of the back-sight. The eye-piece of the observation
glass is so made that it can be turned through a vertical plane
in proportion as the angle of fire increases in relation to the
horizontal. The determination of the distance from the objective
and from the corresponding back-sight as well as the observation
of the altitude is carried out with the aid of the telemeter.
This again carries an observation glass fitted with an eye-piece
which can be turned in the vertical plane in the same manner as
that of the fore-sight. By means of this ingenious sighting
device it is possible to ascertain the range and angle of fire
very easily and speedily.

The weight of the special Krupp anti-aircraft field-piece,
exclusive of the protecting shield, is approximately identical
with that of the ordinary light artillery field-piece. It throws
a shell weighing 8.8 pounds with an initial velocity of about
2,066 feet per second.

Although the German armament manufacturers were among the first
to enter the field with an anti-aircraft gun of this character
they were speedily followed by the French, who devised a superior
weapon. In fact, the latter represented such a decisive advance
that the German artillerists did not hesitate to appropriate
their improvements in sundry essential details, and to
incorporate them with their own weapons. This applies especially
to the differential recoil system which is utilised in the small
anti-aircraft guns now mounted upon the roofs of high buildings
of cities throughout Germany for the express purpose of repelling
aerial attack.

The French system is admitted by the leading artillery
technicians of the world to be the finest which has ever been
designed, its remarkable success being due to the fact that it
takes advantage of the laws of Nature. In this system the gun is
drawn back upon its cradle preparatory to firing. In some
instances the barrel is compressed against a spring, but in the
more modern guns it is forced to rest against a cushion of
compressed air contained within a cylinder. When first bringing
the gun into action, the barrel is brought into the preliminary
position by manually compressing the air or spring by means of a
lever. Thereafter the gun works automatically. When the gun is
fired the barrel is released and it flies forward. At a critical
point in its forward travel the charge is fired and the
projectile speeds on its way. The kick or recoil serves to
arrest the forward movement of the barrel and finally drives it
back again against the strong spring or cushion of compressed air
within the cylinder to its normal position, when it is ready for
the introduction of the next shell.

The outstanding feature of this system is that the projectile is
given a higher initial velocity than is possible with the barrel
held rigid at the moment of discharge, because the shell is
already travelling at the moment of firing.

The fixed anti-aircraft guns such as are stationed upon eminences
and buildings are of the quick firing type, the object being to
hurl a steady, con tinuous stream of missiles upon the swiftly
moving aeroplane. Some of the weapons throw a one-pound shell
and are closely similar to the pom-pom which proved so effective
during the South African war. Machine guns also have been
extensively adopted for this duty by all the combatants, their
range of approximately 2,000 yards and rapidity of fire being
distinctly valuable when hostile aircraft descend to an altitude
which brings them within the range of the weapon.

The greatest difficulty in connection with this phase of
artillery, however, is not so much the evolution of a serviceable
and efficient type of gun, as the determination of the type of
projectile which is likely to be most effective. While shrapnel
is employed somewhat extensively it has not proved completely
satisfactory. It is difficult to set the timing fuse even after
the range has been found approximately, which in itself is no
easy matter when the aircraft is moving rapidly and irregularly,
but reliance is placed thereon in the hope that the machine may
happen to be within the cone of dispersion when the shell bursts,
and that one or more of the pieces of projectile and bullets may
chance to penetrate either the body of the airman or a vital part
of the mechanism.

It is this uncertainty which has led to a preference for a direct
missile such as the bullet discharged from a machine gun. A
stream of missiles, even of rifle calibre, maintained at the rate
of some 400 shots per minute is certain to be more effective,
provided range and aim are correct, than shrapnel. But the
ordinary rifle-bullet, unless the objective is within very close
range, is not likely to cause much harm, at least not to the
mechanism of the aerial vessel.

It is for this reason that greater attention is being devoted,
especially by the French artillerists, to the Chevalier
anti-aircraft gun, a weapon perfected by a Swiss technician
resident in Great Britain. It projects a formidable missile
which in fact is an armour-piercing bullet 1/2- to 3/4-inch in
diameter. It is designed for use with an automatic machinegun,
which the inventor has devised more or less upon the well-known
French system. The bullet has a high velocity--about 2,500 feet
per second--and a maximum range of 6,000 to 8,000 feet at the
maximum elevation. Should such a missile strike the motor or
other mechanism of the vessel it would wreak widespread havoc,
and probably cause the machine to come to earth. This arm has
been designed for the express purpose of disabling the aeroplane,
and not for the subjugation of the airman, which is a minor
consideration, inasmuch as he is condemned to a descent when his
craft receives a mortal wound.

Attempts have been and still are being made to adapt an explosive
projectile to this gun, but so far the measure of success
achieved has not proved very promising. There are immense
difficulties connected with the design of an explosive shell of
this class, charged with a high explosive, especially in
connection with the timing. So far as dependence upon percussive
detonation is concerned there is practically no difficulty.
Should such a missile strike, say, the motor of an aeroplane, or
even the hull of the craft itself, the latter would be
practically destroyed. But all things considered, it is
concluded that more successful results are likely to be achieved
by the armour-piercing bullet striking the mechanism than by an
explosive projectile.

The Krupp company fully reahsed the difficulties pertaining to
the projectile problem in attacks upon aerial craft. So far as
dirigibles are concerned shrapnel is practically useless,
inasmuch as even should the bag be riddled by the flying
fragments, little effective damage would be wrought--the craft
would be able to regain its haven. Accordingly efforts were
concentrated upon the perfection of two new types of projectiles,
both of which were directed more particularly against the
dirigible. The one is the incendiary shell--obus fumigene--while
the other is a shell, the contents of which, upon coming into
contact with the gas contained within the gas-bag, set up certain
chemical reactions which precipitate an explosion and fire.

The incendiary shells are charged with a certain compound which
is ignited by means of a fuse during its flight. This fuse
arrangement coincides very closely with that attached to ordinary
shrapnel, inasmuch as the timing may be set to induce ignition
at different periods, such as either at the moment it leaves the
gun, before, or when it strikes the envelope of the dirigible.
The shell is fitted with a "tracer," that is to say, upon
becoming ignited it leaves a trail of smoke, corresponding with
the trail of a rocket, so that its passage through the air may be
followed with facility. This shell, however, was designed to
fulfil a dual. Not only will it fire the gaseous contents out of
the dirigible, but it has an explosive effect upon striking an
incombustible portion of the aircraft, such as the machinery,
propellers or car, when it will cause sufficient damage to throw
the craft out of action.

The elaborate trials which were carried out with the obus
fumigene certainly were spectacular so as they went. Two small
spherical balloons, 10 feet in diameter, and attached to 1,000
feet of cable, were sent aloft. The anti-aircraft guns
themselves were placed about 5,1OO feet distant. Owing to the
inclement weather the balloons were unable to attain a height of
more than 200 feet in a direct vertical line above the ground.
The guns were trained and fired, but the one balloon was not hit
until the second round, while the third escaped injury until the
fifth round. When struck they collapsed instantly. Though the
test was not particularly conclusive, and afforded no reliable
data, one point was ascertained--the trail of smoke emitted by
the shell enabled its trajectory to be followed with ease. Upon
the conclusion of these trials, which were the most successful
recorded, quick-firing tests in the horizontal plane were carried
out. The best performance in this instance was the discharge of
five rounds in eight seconds. In this instance the paths of the
projectiles were simple and easy to follow, the flight of the
shell being observed until it fell some 18,670 feet away. But
the Krupp firmhave found that trials upon the testing ground with
a captive balloon differ very materially from sterntests in the
field of actual warfare. Practically nothing has been heard of
the two projectiles during this war, as they have proved an
absolute failure.

Some months ago the world was startled by the announcement that
the leading German armament firm had acquired the whole of the
interest in an aerial torpedo which had been evolved by the
Swedish artillerist, Gustave Unge, and it was predicted that in
the next war widespread havoc would be wrought therewith.
Remarkable claims were advanced for this projectile, the foremost
being that it would travel for a considerable distance through
the air and alight upon the objective with infallible accuracy.
The torpedo in question was subjected to exacting tests in Great
Britain, which failed to substantiate all the claims which were
advanced, and it is significant to observe that little has been
heard of it during the present conflict. It is urged in certain
technical quarters, however, that the aerial torpedo will prove
to be the most successful projectile that can be used against
aircraft. I shall deal with this question in a later chapter.

During the early days of the war anti-aircraft artillery appeared
to be a much overrated arm. The successes placed to its credit
were insignificant. This was due to the artillerymen being
unfamiliar with the new arm, and the conditions which prevail
when firing into space. Since actual practice became possible
great advances in marksmanship have been recorded, and the
accuracy of such fire to-day is striking. Fortunately the airman
possesses the advantage. He can manoeuvre beyond the range of
the hostile weapons. At the moment 10,000 feet represents the
extreme altitude to which projectiles can be hurled from the arms
of this character which are now in use, and they lack
destructiveness at that range, for their velocity is virtually
expended.

Picking up the range is still as difficult as ever. The practice
followed by the Germans serves to indicate the Teuton
thoroughness of method in attacking such problems even if success
does not ensue. The favourite German principle of disposing
anti-aircraft artillery is to divide the territory to be
protected into equilateral triangles, the sides of which have a
length of about six miles or less, according to the maximum
effective range of the pieces at an elevation of 23 1/2 degrees.

The guns are disposed at the corners of the triangles as
indicated in Figs. 13-14. Taking the one triangle as an example,
the method of picking up the range may be explained as follows.
The several guns at the comers of the triangle, each of which can
be trained through the 360 degrees in the horizontal plane, are
in telephonic touch with an observer O stationed some distance
away. The airman A enters the area of the triangle. The
observer takes the range and communicates with the gunner B, who
fires his weapon. The shell bursts at 1 emitting a red flame and
smoke. The observer notes the altitude and relative position of
the explosion in regard to the aircraft, while gunner B himself
observes whether the shell has burst to the right or to the left
of the objective and corrects accordingly. The observer commands
C to fire, and another shell is launched which emits a yellow
flame and smoke. It bursts at 2 according to the observer, while
gunner C also notes whether it is to the right or to the left of
the target and corrects accordingly. Now gunner D receives the
command to fire and the shell which explodes at 3 throws off a
white flame and smoke. Gunner D likewise observes whether there
is any deviation to right or left of the target and corrects in a
similar manner. From the sum of the three rounds the observer
corrects the altitude, completes his calculations, and
communicates his instructions for correction to the three
gunners, who now merely train their weapons for altitude. The
objective is to induce the shells hurled from the three corners
of the triangle to burst at a common point 4, which is considered
to be the most critical spot for the aviator. The fire is then
practically concentrated from the three weapons upon the apex of
a triangular cone which is held to bring the machine within the
danger zone.

This method of finding the range is carried out quickly--two or
three seconds being occupied in the task. In the early days of
the war the German anti-aircraft artillerymen proved sadly
deficient in this work, but practice improved their fire to a
marvellous degree, with the result that at the moment it is
dangerous for an aviator to essay his task within an altitude of
6,000 feet, which is the range of the average anti-aircraft gun.

The country occupied by a belligerent is divided up in this
manner into a series of triangles. For instance, a machine
entering hostile territory from the east, enters the triangle
A-B-C, and consequently comes within the range of the guns posted
at the comers of the triangle. Directly he crosses the line B-C
and enters the adjacent triangle he passes beyond the range of
gun A but comes within the range of the gun posted at D, and
while within the triangular area is under fire from the guns
B-C-D. He turns and crosses the line A-C, but in so doing enters
another triangle A-C-E, and comes range of the gun posted at E.

The accompanying diagram represents an area of country divided up
into such triangle and the position of the guns, while the circle
round the latter indicate the training arc of the weapons, each
of which is a complete circle, in the horizontal plane. The
dotted line represents the aviator's line of flight, and it will
be seen that no matter how he twists and turns he is always
within the danger zone while flying over hostile territory. The
moment he outdistances one gun he comes within range of another.

The safety of the aviator under these circumstances depends upon
his maintaining an altitude exceeding the range of the guns
below, the most powerful of which have a range of 8,000 to 10,000
feet, or on speed combined with rapid twisting and turning, or
erratic undulating flight, rendering it extremely difficult for
the gun-layer to follow his path with sufficient celerity to
ensure accurate firing.

At altitudes ranging between 4,000 and 6,000 feet the aeroplane
comes within the range of rifle and machine-gun firing. The
former, however, unless discharged in volleys with the shots
covering a wide area, is not particularly dangerous, inasmuch as
the odds are overwhelmingly against the rifleman. He is not
accustomed to following and firing upon a rapidly moving
objective, the result being that ninety-nine times out of a
hundred he fails to register a hit. On the other hand the
advantage accruing from machine-gun fire is, that owing to the
continuous stream of bullets projected, there is a greater
possibility of the gun being trained upon the objective and
putting it hors de combat.

But, taking all things into consideration, and notwithstanding
the achievements of the artillerist, the advantages are
overwhelmingly on the side of the aviator. When one reflects
upon the total sum of aircraft which have been brought to earth
during the present campaign, it will be realised that the number
of prizes is insignificant in comparison with the quantity of
ammunition expended.

CHAPTER XVI
MINING THE AIR

While the anti-aircraft gun represents the only force which has
been brought to the practical stage for repelling aerial attack,
and incidentally is the sole offensive weapon which has
established its effectiveness, many other schemes have been
devised and suggested to consummate these ends. While some of
these schemes are wildly fantastic, others are feasible within
certain limitations, as for instance when directed against
dirigibles.

It has been argued that the atmosphere is akin to the salt seas;
that an aerial vessel in its particular element is confronted
with dangers identical with those prevailing among the waters of
the earth. But such an analogy is fallacious: there is no more
similarity between the air and the ocean than there is between an
airship and a man-of-war. The waters of the earth conceal from
sight innumerable obstructions, such as rocks, shoals, sandbanks,
and other dangers which cannot by any means be readily detected.

But no such impediments are encountered in the ether. The craft
of the air is virtually a free age in the three dimensions. It
can go whither it will without let or hindrance so long as the
mechanical agencies of man are able to cope with the influences
of Nature. It can ascend to a height which is out of all
proportion to the depth to which the submarine can descend in
safety. It is a matter of current knowledge that a submarine
cannot sink to a depth of more than 250 feet: an aerial vessel is
able to ascend to 5,000, 8,000, or even 10,000 feet above the
earth, and the higher the altitude it attains the greater is its
degree of safety. The limit of ascension is governed merely by
the physical capacities of those who are responsible for the
aerial vessel's movement.

It is for this reason that the defensive measures which are
practised in the waters of the earth are inapplicable to the
atmosphere. Movement by, or in, water is governed by the depth
of channels, and these may be rendered impassable or dangerous to
negotiate by the planting of mines. A passing ship or submarine
may circumvent these explosive obstructions, but such a
successful manoeuvre is generally a matter of good luck. So far
as submarines are concerned the fact must not be over looked that
movements in the sea are carried out under blind conditions: the
navigator is unable to see where he is going; the optic faculty
is rendered nugatory. Contrast the disability of the submarine
with the privileges of its consort in the air. The latter is
able to profit from vision. The aerial navigator is able to see
every inch of his way, at least during daylight. When darkness
falls he is condemned to the same helplessness as his confrere in
the waters below.

A well-known British authority upon aviation suggested that
advantage should be taken of this disability, and that the air
should be mined during periods of darkness and fog to secure
protection against aerial invasion. At first sight the proposal
appears to be absolutely grotesque, but a little reflection will
suffice to demonstrate its possibilities when the area to be
defended is comparatively limited. The suggestion merely
proposes to profit from one defect of the dirigible. The latter,
when bent upon a daring expedition, naturally prefers to make a
bee-line towards its objective: fuel considerations as a matter
of fact compel it to do so. Consequently it is possible, within
certain limits, to anticipate the route which an invading craft
will follow: the course is practically as obvious as if the
vessel were condemned to a narrow lane marked out by sign-posts.
Moreover, if approaching under cover of night or during thick
weather, it will metaphorically "hug the ground." To attempt to
complete its task at a great height is to court failure, as the
range of vision is necessarily so limited.

Under these circumstances the mining of the air could be carried
out upon the obvious approaches to a threatened area. The mines,
comprising large charges of high-explosive and combustible
material, would be attached to small captive balloons similar to
the "sounding balloons" which are so much used by meteorologists
in operations for sounding the upper strata of the atmosphere.
These pilot balloons would be captive, their thin wires being
wound upon winches planted at close intervals along the
coast-line. The balloon-mines themselves would be sent to
varying heights, ranging from 1,000 to 5,000 feet, and with
several attached to each cable, the disposition of the mines
in the air in such an irregular manner being in fact closely
similar to the practice adopted in the mining of a channel for
protection against submarines and hostile ships.

The suggestion is that these mines should be sent aloft at dusk
or upon the approach of thick and foggy weather, and should be
wound in at dawn or when the atmosphere cleared, inasmuch as in
fine weather the floating aerial menace would be readily detected
by the pilot of a dirigible, and would be carefully avoided. If
the network were sufficiently intricate it would not be easy for
an airship travelling at night or in foggy weather to steer clear
of danger, for the wires holding the balloons captive would be
difficult to distinguish.

The mines would depend upon detonators to complete their work,
and here again they would bear a close resemblance to sea-mines.
By looping the mines their deadliness could be increased. The
unsuspicious airship, advancing under cover of darkness or thick
weather, might foul one of the wires, and, driving forward, would
tend to pull one or more mines against itself. Under the force
of the impact, no matter how gentle, or slight, one or more of
the detonating levers would be moved, causing the mine to
explode, thus bursting the lifting bag of the vessel, and firing
its gaseous contents. An alternative method, especially when a
cable carried only a single mine, would be to wind in the captive
balloon directly the wire was fouled by an invading aerial craft,
the process being continued until the mine was brought against
the vessel and thereby detonated.

Another proposed mining method differs materially in its
application. In this instance it is suggested that the mines
should be sent aloft, but should not be of the contact type, and
should not be fired by impact detonators, but that dependence
should be placed rather upon the disturbing forces of a severe
concussion in the air. The mines would be floating aoft, and
the advance of the airship would be detected. The elevation
of the mines in the vicinity of the invading craft would be
known, while the altitude of the airship in relation thereto
could be calculated. Then, it is proposed that a mine within d
certain radius of the approaching craft, and, of course, below
it, should be fired electrically from the ground. It is
maintained that if the charge were sufficiently heavy and an
adequate sheet of flame were produced as a result of the
ignition, an airship within a hundred yards thereof would be
imperilled seriously, while the other mines would also be fired,
communicating ignition from one to the other. The equilibrium
of the airship is so delicate that it can be readily upset, and
taking into account the facts that gas is always exuding from
the bag, and that hydrogen has a tendency to spread somewhat in
the manner of oil upon water, it is argued that the gas would be
ignited, and would bring about the explosion of the airship.

Another method has even been advocated. It is averred in
authoritative circles that when the aerial invasion in force of
Great Britain is attempted, the Zeppelins will advance under the
cover of clouds. Also that the craft will make for one
objective--London. Doubtless advantage will be taken of clouds,
inasmuch as they will extend a measure of protection to the craft,
and will probably enable the invading fleet to elude the vigilance
of the aeroplane scouts and patrols. Under these circumstances it
is suggested that balloon-mines should be sent aloft and be
concealed in the clouds. It would be impossible to detect the
wires holding them captive, so that the precise location of the
lurking danger would not be divined by the invader. Of course,
the chances are that the invading airship would unconsciously
miss the mines; on the other hand the possibilities are equally
great that it would blunder into one of these traps and be blown
to atoms.

An English airman has recently suggested a means of mining
invading Zeppelins which differs completely from the foregoing
proposals. His idea is that aeroplanes should be equipped with
small mines of the contact type, charged with high explosives,
and that the latter should be lowered from the aeroplane and be
trawled through the atmosphere. As an illustration I will suppose
that a hostile aircraft is sighted by a patrolling aeroplane.
The pilot's companion in the latter immediately prepares his
aerial mine, fixing the detonator, and attaching the mine to the
wire. The latter is then dropped overboard, the wire being paid
out from a winch until it has descended to the level of the
hostile craft. The airman now manoeuvres in the air circling
about the airship, dragging his mine behind him, and endeavouring
to throw it across or to bring it into contact with the airship
below. Naturally the latter, directly it observed the airman's
object, would endeavour to elude the pursuing trawling mine,
either by crowding on speed or by rising to a greater altitude.
The aeroplane, however, would have the advantage both in point of
speed and powers of climbing, while there is no doubt that the
sight of the mine swinging in the air would exert a decisive
moral effect upon those in the airship.

Attempts to render the mine harmless by discharging it
prematurely with the aid of rifle and machine-gun fire would, of
course, be made by the crew of the airship, but the trawling mine
would prove a very difficult target to strike. If such a missile
were used against an airship of the proportions of a Zeppelin the
mine would inevitably be trawled across the vessel sooner or
later. Once the airship had been fouled, the aviator would
merely have to drive ahead, dragging the wire and its charge
across the gas-bag until at last one of the contact levers of the
mine was moved by being dragged against some part of the vessel,
when the mine would be exploded. In such operations the aviator
would run a certain risk, as he would be more or less above the
airship, and to a certain degree within the zone of the ultimate
explosion. But there is no doubt that he would succeed in his
"fishing" exploit within a very short time.

This ingenious scheme has already been tested upon a small scale
and has been found effective, the trawling bomb being drawn
across its target and fired by contact within a few minutes. The
experiment seems to prove that it would be simpler and more
effectual to attack a hostile aircraft such as a Zeppelin in this
manner than to drop free bombs at random. Moreover, we cannot
doubt that the sight of a mine containing even ten or twelve
pounds of high explosive dangling at the end of a wire would
precipitate a retreat on the part of an airship more speedily
than any other combative expedient.

The advocate of this mine-trawling method, who is a well-known
aviator, anticipates no difficulty in manoeuvring a mine weighing
30 pounds at the end of 300 feet of fine wire. Success depends
in a great measure on the skill of the aviator in maintaining a
constant tension upon the line until it falls across its
objective.

The process calls for a certain manifestation of skill in
manoeuvring the aeroplane in relation to the airship, judgment of
distance, and ability to operate the aeroplane speedily. The
rapid ascensional capability of the airship, as compared with
that of the aeroplane, is a disadvantage, but on the other hand,
the superior mobility and speed of the aeroplane would tell
decisively for success.

Among the many wonders which the Krupp organisation is stated to
have perfected, and which it is claimed will create considerable
surprise, is the aerial torpedo. Many of the Krupp claims are
wildly chimerical, as events have already proved, but there is no
doubt that considerable effort has been expended upon this latest
missile, for which the firm is said to have paid the inventor
upwards of L25,000--$125,000. Curiously enough the projectile
was perfected within gunshot of the British aerodrome of Hendon
and is stated to have been offered to the British Government at
the time, and to have met with a chilling reception. One fact,
however, is well established. The inventor went to Germany, and
submitted his idea to Krupp, by whom it was tested without delay.
Upon the completion of the purchase, the great armament
manufacturers did not fail to publish broadcast the fact that
they had acquired a mysterious new terror of the skies. That was
some three years ago, and in the interval the cleverest brains of
the German firm have been steadily devoting their time and
energies to the improvement of the missile, the first appearance
of which was recorded, in a somewhat hazy manner, in the closing
days of December.

While the exact mechanism of this missile is a secret, the
governing principles of its design and operation are known to a
select few technicians in this country. Strange to say, the
projectile was designed in the first instance in the interests of
peace and humanty, but while engaged upon his experiments the
inventor suddenly concluded that it would be a more profitable
asset if devoted to the grim game of war. At the time the
military significance of the airship and the aeroplane were
becoming apparent; hence the sudden diversion of the idea into a
destructive channel.

This aerial torpedo is a small missile carrying a charge of high
explosive, such as trinitrotoluene, and depends for its
detonation upon impact or a time fuse. It is launched into the
air from a cradle in the manner of the ordinary torpedo, but the
initial velocity is low. The torpedo is fitted with its own
motive power, which comes automatically into action as the
missile climbs into the air. This self-contained energy is so
devised that the maximum power is attained before the missile has
lost the velocity imparted in the first instance, the result
being that it is able to continue its flight in a horizontal
direction from the moment it attains the highest point in its
trajectory, which is naturally varied according to requirements.
But there is no secret about the means of propulsion. The body
is charged with a slow-burning combustible, in the manner of the
ordinary rocket, whereby it is given a rapid rotary motion.

Furthermore it is stated to be fitted with a small gyroscope in
the manner of the torpedo used in the seas, for the purpose of
maintaining direction during flight, but upon this point there is
considerable divergence of opinion among technicians, the general
idea being that the torpedo depends upon an application of the
principle of the ordinary rocket rather than upon a small engine
such as is fitted to the ordinary torpedo. The employment of a
slow combustible ensures the maintenance of the missile in the
air for a period exceeding that of the ordinary shell. It is
claimed by the Germans that this projectile will keep aloft for
half-an-hour or more, but this is a phantasy. Its maintenance of
flight is merely a matter of minutes.

The belated appearance of this much-lauded projectile and its
restricted use suggest that it is unreliable, and perhaps no more
effective than the aerial torpedo which appeared in the United
States during the Spanish-American War, and proved a complete
failure. An effective and reliable means of combating or
frustrating a dirigible attack, other than by gun-fire or resort
to the drastic remedy of ramming the enemy, has yet to be
devised.

CHAPTER XVII
WIRELESS IN AVIATION

In a previous chapter the various methods of signalling between
the ground and the airman aloft have been described. Seeing that
wireless telegraphy has made such enormous strides and has
advanced to such a degree of perfection, one naturally would
conclude that it constitutes an ideal system of communication
under such conditions in military operations.

But this is not the case. Wireless is utilised only to a very
limited extent. This is due to two causes. The one is of a
technical, the other of a strategical character.

The uninitiated, bearing in mind the comparative ease with which
wireless installations may be established at a relatively small
expense, would not unreasonably think that no serious
difficulties of a technical character could arise: at least none
which would defy solution. But these difficulties exist in two
or three different fields, each of which is peculiarly complex
and demands individual treatment.

In the first place, there is the weight of the necessary
installation. In the case of the dirigible this may be a
secondary consideration, but with the aeroplane it is a matter of
primary and vital importance. Again, under present conditions,
the noise of the motor is apt to render the intelligent
deciphering of messages while aloft a matter of extreme
difficulty, especially as these are communicated in code. The
engine noise might be effectively overcome by the use of a
muffler such as, is used with automobiles, but then there is the
further difficulty of vibration.

This problem is being attacked in an ingenious manner. It is
proposed to substitute for audible signals visual
interpretations, by the aid of an electric lamp, the fluctuations
in which would correspond to the dots and dashes of the Morse
code. Thus the airman would read his messages by sight instead
of by sound.

This method, however, is quite in its infancy, and although
attractive in theory and fascinating as a laboratory experiment
or when conducted under experimental conditions, it has not
proved reliable or effective in aeronautical operations. But at
the same time it indicates a promising line of research and
development.

Then there are the problems of weight and the aerial. So far as
present knowledge goes, the most satisfactory form of aerial yet
exploited is that known as the trailing wire. From 300 to 700
feet of wire are coiled upon a reel, and when aloft this wire is
paid out so that it hangs below the aeroplane. As a matter of
fact,when the machine is travelling at high speed it trails
horizontally astern, but this is immaterial. One investigator,
who strongly disapproves of the trailing aerial, has carried out
experiments with a network of wires laid upon and attached to the
surface of the aeroplane's wings. But the trailing wire is
generally preferred, and certainly up to the present has proved
more satisfactory.

The greatest obstacle, however, is the necessary apparatus. The
average aeroplane designed for military duty is already loaded to
the maximum. As a rule it carries the pilot and an observer, and
invariably includes a light arm for defence against an aerial
enemy, together with an adequate supply of ammunition, while
unless short sharp flights are to be made, the fuel supply
represents an appreciable load. Under these circumstances the
item of weight is a vital consideration. It must be kept within
a limit of 100 pounds, and the less the equipment weighs the more
satisfactory it is likely to prove, other things being equal.

The two most successful systems yet exploited are the Dubilier
and the Rouget. The former is an American invention, the latter
is of French origin. Both have been tested by the British
Military Aeronautical Department, and the French authorities
have subjected the French system to rigorous trials. Both
systems, within their limitations, have proved satisfactory.

The outstanding feature of the Dubilier system is the production
of sine waves of musical frequency from continuous current, thus
dispensing with the rotary converter. The operating principle is
the obtaining of a series of unidirectional impulses by a
condenser discharge, the pulsating currents following one another
at regular intervals at a frequency of 500 impulses per second,
which may be augmented up to 1,000 impulses per second. The
complete weight of such an apparatus is 40 pounds; the electric
generator, which is no larger than the motor used for driving the
ordinary table ventilating fan, accounts for 16 pounds of this
total. Under test at sea, upon the deck of a ship, a range of
250 miles has been obtained. The British Government carried out
a series of experiments with this system, using a small plant
weighing about 30 pounds, with which communication was maintained
up to about 20 miles.

In the French system the Reuget transmitter is employed. The
apparatus, including the dynamo, which is extremely small, weighs
in all 70 pounds. A small alternator of 200 watts and 100 volts
is coupled direct to the aeroplane motor, a new clutch coupler
being employed for this purpose. By means of a small transformer
the voltage is raised to 30,000 volts, at which the condenser is
charged. In this instance the musical spark method is employed.

The whole of the high tension wiring is placed within a small
space so as not to endanger the pilot, while the transformer is
hermetically sealed in a box with paraffin. The aerial comprises
a trailing wire 100 feet in length, which, however, can be
wound in upon its reel within 15 seconds. This reeled antenna,
moreover, is fitted with a safety device whereby the wire can be
cut adrift in the event of an accident befalling the aeroplane
and necessitating an abrupt descent. With this apparatus the
French authorities have been able to maintain communication over
a distance of 30 miles.

In maintaining ethereal communication with aeroplanes, however, a
portable or mobile station upon the ground is requisite, and this
station must be within the radius of the aerial transmitter, if
messages are to be received from aloft with any degree of
accuracy and reliability. Thus it will be recognised that the
land station is as important as the aeroplane equipment, and
demands similar consideration.

A wide variety of systems have been employed to meet these
conditions. There is the travelling automobile station, in which
the installation is mounted upon a motor-car. In this instance
the whole equipment is carried upon a single vehicle, while the
antenna is stowed upon the roof and can be raised or lowered
within a few seconds. If motor traction is unavailable, then
animal haulage may be employed, but in this instance the
installation is divided between two vehicles, one carrying the
transmitting and receiving apparatus and the generating plant,
the other the fuel supplies and the aerial, together with spare
parts.

The motive power is supplied by a small air cooled petrol or
gasoline motor developing eight horse-power, and coupled direct
to a 2-kilo watt alternator. At one end of the shaft of the
latter the disk discharger is mounted, its function being to
break up the train of waves into groups of waves, so as to impart
a musical sound to the note produced in the receiver. A flexible
cable transmits the electric current from the generator to the
wagon containing the instruments. The aerial is built up of
masts carried in sections.

The Germans employ a mobile apparatus which is very similar, but
in this instance the mast is telescopic. When closed it occupies
but little space. By turning the winch handle the mast is
extended, and can be carried to any height up to a maximum of
about 100 feet. The capacity of these mobile stations varies
within wide limits, the range of the largest and most powerful
installations being about 200 miles. The disadvantage of these
systems, however, is that they are condemned to territories where
the ground at the utmost is gently undulating, and where there
are roads on which four-wheeled vehicles can travel.

For operation in hilly districts, where only trails are to be
found, the Marconi Company, has perfected what may be described
as "pack" and "knapsack" installations respectively. In the
first named the whole of the installation is mounted upon the
backs of four horses. The first carries the generator set, the
second the transmitting instruments, the third the receiving
equipment, and the fourth the detachable mast and stays.

The generator is carried upon the horse's saddle, and is fitted
with a pair of legs on each side. On one side of the saddle is
mounted a small highspeed explosion motor, while on the opposite
side, in axial alignment with the motor, is a small dynamo. When
it is desired to erect the installation the saddle carrying this
set is removed from the horse's back and placed upon the ground,
the legs acting as the support. A length of shaft is then
slipped into sockets at the inner ends of the motor and dynamo
shafts respectively, thus coupling them directly, while the
current is transmitted through a short length of flexible cable
to the instruments. The mast itself is made in lengths of about
four feet, which are slipped together in the manner of the
sections of a fishing rod, and erected, being supported by means
of wire guys. In this manner an antenna from 40 to 50 feet in
height may be obtained.

The feature of this set is its compactness, the equal division of
the sections of the installation, and the celerity with which the
station may be set up and dismantled in extremely mountainous
country such as the Vosges, where it is even difficult for a
pack-horse to climb to commanding or suitable positions, there is
still another set which has been perfected by the Marconi
Company. This is the "knapsack" set, in which the whole of the
installation, necessarily light, small, and compact, is divided
among four men, and carried in the manner of knapsacks upon their
backs. Although necessarily of limited radius, such an
installation is adequate for communication within the restricted
range of air-craft.

Greater difficulties have to be overcome in the mounting of a
wireless installation upon a dirigible. When the Zeppelin was
finally accepted by the German Government, the military
authorities emphasised the great part which wireless telegraphy
was destined to play in connection with such craft. But have
these anticipations been fulfilled? By no means, as a little
reflection will suffice to prove.

In the first place, a wireless outfit is about the most dangerous
piece of equipment which could be carried by such a craft as the
Zeppelin unless it is exceptionally well protected. As is well
known the rigidity of this type of airship is dependent upon a
large and complicated network of aluminium, which constitutes the
frame. Such a huge mass of metal constitutes an excellent
collector of electricity from the atmosphere; it becomes charged
to the maximum with electricity.

In this manner a formidable contributory source of danger to the
airship is formed. In fact, this was the reason why "Z-IV"
vanished suddenly in smoke and flame upon falling foul of the
branches of trees during its descent. At the time the Zeppelin
was a highly charged electrical machine or battery as it were,
insulated by the surrounding air. Directly the airship touched
the trees a short circuit was established, and the resultant
spark sufficed to fire the gas, which is continuously exuding
from the gas bags.

After this accident minute calculations were made and it was
ascertained that a potential difference of no less than 100,00
volts existed between the framework of the dirigible and the
trees. This tension sufficed to produce a spark 4 inches in
length. It is not surprising that the establishment of the
electric equilibrium by contact with the trees, which produced
such a spark should fire the hydrogen inflation charge. In fact
the heat generated was so intense that the aluminium metallic
framework was fused. The measurements which were made proved
that the gas was consumed within 15 seconds and the envelope
destroyed within 20 seconds.

As a result of this disaster endeavours were made to persuade
Count Zeppelin to abandon the use of aluminium for the framework
of his balloon but they were fruitless, a result no doubt due to
the fact that the inventor of the airship of this name has but a
superficial knowledge of the various sciences which bear upon
aeronautics, and fully illustrates the truth of the old adage
that "a little learning is a dangerous thing." Count Zeppelin
continues to work upon his original lines, but the danger of his
system of construction was not lost upon another German
investigator, Professor Schiitte, who forthwith embarked upon the
construction of another rigid system, similar to that of
Zeppelin, at Lanz. In this vessel aluminium was completely
abandoned in favour of a framework of ash and poplar.

The fact that the aluminium constituted a dangerous collector of
electricity rendered the installation of wireless upon the
Zeppelin not only perilous but difficult. Very serious
disturbances of an electrical nature were set up, with the result
that wireless communication between the travelling dirigible and
the ground below was rendered extremely uncertain. In fact, it
has never yet been possible to communicate over distances
exceeding about 150 miles. Apart from this defect, the danger of
operating the wireless is obvious, and it is generally believed
in technical circles that the majority of the Zeppelin disasters
from fire have been directly attributable to this, especially
those disasters which have occurred when the vessel has suddenly
exploded before coming into contact with terrestrial
obstructions.

In the later vessels of this type the wireless installation is
housed in a well insulated compartment. This insulation has been
carried, to an extreme degree, which indicates that at last the
authorities have recognised the serious menace that wireless
offers to the safety of the craft, with the result that every
protective device to avoid disaster from this cause has been
freely adopted.

The fact that it is not possible to maintain cornmunication over
a distance exceeding some 20 miles is a severe handicap to the
progressive development of wireless telegraphy in this field. It
is a totally inadequate radius when the operations of the present
war are borne in mind. A round journey of 200, or even more
miles is considered a mere jaunt; it is the long distance flight
which counts, and which contributes to the value of an airman's
observations. The general impression is that the fighting line
or zone comprises merely two or three successive stretches of
trenches and other defences, representing a belt five miles or so
in width, but this is a fallacy. The fighting zone is at least
20 miles in width; that is to say, the occupied territory in
which vital movements take place represents a distance of 20
miles from the foremost line of trenches to the extreme rear,
and then comes the secondary zone, which may be a further 10
miles or more in depth. Consequently the airman must fly at
least 30 miles in a bee-line to cover the transverse belt of the
enemy's field of operations. Upon the German and Russian sides
this zone is of far greater depth, ranging up to 50 miles or so
in width. In these circumstances the difficulties of ethereal
communication 'twixt air and earth may be realised under the
present limitations of radius from which it is possible to
transmit.

But there are reasons still more cogent to explain why wireless
telegraphy has not been used upon a more extensive scale during
the present campaign. Wireless communication is not secretive.
In other words, its messages may be picked up by friend and foe
alike with equal facility. True, the messages are sent in code,
which may be unintelligible to the enemy. In this event the
opponent endeavours to render the communications undecipherable
to one and all by what is known as "jambing." That is to say, he
sends out an aimless string of signals for the purpose of
confusing senders and receivers, and this is continued without
cessation and at a rapid rate. The result is that messages
become blurred and undecipherable.

But there is another danger attending the use of wireless upon
the battlefield. The fact that the stations are of limited range
is well known to the opposing forces, and they are equally well
aware of the fact that aerial craft cannot communicate over long
distances. For instance, A sends his airmen aloft and
conversation begins between the clouds and the ground. Presently
the receivers of B begin to record faint signals. They fluctuate
in intensity, but within a few seconds B gathers that an
aeroplane is aloft and communicating with its base. By the aid
of the field telephone B gets into touch with his whole string of
wireless stations and orders a keen look-out and a listening ear
to ascertain whether they have heard the same signals. Some
report that the signals are quite distinct and growing louder,
while others declare that the signals are growing fainter and
intermittent. In this manner B is able to deduce in which
direction the aeroplane is flying. Thus if those to the east
report that signals are growing stronger, while the stations on
the west state that they are diminishing, it is obvious that the
aeroplane is flying west to east, and vice versa when the west
hears more plainly at the expense of the east. If, however, both
should report that signals are growing stronger, then it is
obvious that the aircraft is advancing directly towards them.

It was this ability to deduce direction from the sound of the
signals which led to the location of the Zeppelin which came down
at Lun6ville some months previous to the war, and which
threatened to develop into a diplomatic incident of serious
importance. The French wireless stations running south-east to
north-west were vigilant, and the outer station on the north-west
side picked up the Zeppelin's conversation. It maintained a
discreet silence, but communicated by telephone to its colleagues
behind.

Presently No. 2 station came within range, followed by Nos. 3, 4,
5, 6, and so on in turn. Thus the track of the Zeppelin was
dogged silently through the air by its wireless conversation as
easily and as positively as if its flight had been followed by
the naked eye. The Zeppelin travellers were quite ignorant of
this action upon the part of the French and were surprised when
they were rounded-up to learn that they had been tracked so
ruthlessly. Every message which the wireless of the Zeppelin had
transmitted had been received and filed by the French.

Under these circumstances it is doubtful whether wireless
telegraphy between aircraft and the forces beneath will be
adopted extensively during the present campaign. Of course,
should some radical improvement be perfected, whereby
communication may be rendered absolutely secretive, while no
intimation is conveyed to the enemy that ethereal conversation is
in progress, then the whole situation will be changed, and there
may be remarkable developments.

CHAPTER XVIII
AIRCRAFT AND NAVAL OPERATIONS

When once the flying machine had indicated its possibilities in
connection with land operations it was only natural that
endeavours should be made to adapt it to the more rigorous
requirements of the naval service. But the conditions are so
vastly dissimilar that only a meagre measure of success has been
recorded. Bomb-throwing from aloft upon the decks of battleships
appeals vividly to the popular imagination, and the widespread
destruction which may be caused by dropping such an agent down
the funnel of a vessel into the boiler-room is a favourite theme
among writers of fiction and artists. But hitting such an
objective while it is tearing at high speed through the water,
from a height of several thousand feet is a vastly different task
from throwing sticks and balls at an Aunt Sally on terra firma:
the target is so small and elusive.

Practically it is impossible to employ the flying machine,
whether it be a dirigible or an aeroplane, in this field. Many
factors militate against such an application. In the first place
there is a very wide difference between dry land and a stretch of
water as an area over which to manoeuvre. So far as the land is
concerned descent is practicable at any time and almost anywhere.
But an attempt to descend upon the open sea even when the latter
is as calm as the proverbial mill-pond is fraught with
considerable danger. The air-currents immediately above the
water differ radically from those prevailing above the surface of
the land. Solar radiation also plays a very vital part. In fact
the dirigible dare not venture to make such a landing even if it
be provided with floats. The chances are a thousand to one that
the cars will become water-logged, rendering re-ascent a matter
of extreme difficulty, if not absolutely impossible. On the
other hand, the aeroplane when equipped with floats, is able to
alight upon the water, and to rest thereon for a time. It may
even take in a new supply of fuel if the elements be propitious,
and may be able to re-ascend, but the occasions are rare when
such operations can be carried out successfully.

In operations over water the airman is confronted with one
serious danger--the risk of losing his bearings and his way. For
instance, many attempts have been made to cross the North Sea by
aeroplane, but only one has proved successful so far. The
intrepid aviator did succeed in passing from the shore of Britain
to the coast of Scandinavia. Many people suppose that because an
airman is equipped with a compass he must be able to find his
way, but this is a fallacy. The aviator is in the same plight as
a mariner who is compelled from circumstances to rely upon his
compass alone, and who is debarred by inclement weather from
deciding his precise position by taking the sun. A ship
ploughing the waters has to contend against the action of cross
currents, the speed of which varies considerably, as well as
adverse winds. Unless absolute correction for these influences
can be made the ship will wander considerably from its course.
The airman is placed in a worse position. He has no means of
determining the direction and velocity of the currents prevailing
in the atmosphere, and his compass cannot give him any help in
this connection, because it merely indicates direction.

Unless the airman has some means of determining his position,
such as landmarks, he fails to realise the fact that he is
drifting, or, even if he becomes aware of this fact, it is by no
means a simple straightforward matter for him to make adequate
allowance for the factor. Side-drift is the aviator's greatest

Book of the day: