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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 wroughtthe 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 shellobus fumigenewhile
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 ascertainedthe 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 obje