ted by the inclination of the
aeroplane when climbing, while the facility with which the weapon may be
moved through the horizontal plane is distinctly favourable.

But the aerial marksman suffers from one very pronounced defect: he has
a severely restricted survey of everything below, since his vision is
interrupted by the planes. The result is that an enemy who has lost
ascendancy of position is comparatively safe if he is able to fly
immediately below his adversary: the mitrailleuse of the latter cannot
be trained upon him. On the other hand the enemy, if equipped with
repeating rifles or automatic pistols, is able to inflict appreciable
damage upon the craft overhead, the difficulties of firing vertically
into the air notwithstanding.

In the Vickers system, where the propeller is mounted behind the car,
the aeroplane thus operating upon the pusher principle, the nose of the
car is occupied by the arm, which is a rifle calibre machine gun fitted
upon a special mounting. The prow is provided with an embrasure for
the weapon and the latter is so installed as to command an angle of 30
degrees on all sides of the longitudinal axis of the machine when
in flight. In this instance the marksman is provided with complete
protection on all sides, inasmuch as his position is in the prow, where
the hood of the fo'c's'le shields him from overhead attack. The gun
is protected by a special shield which moves with the gun barrel. This
shield is provided with mica windows, through which the gunner is able
to sight his arm, so that he is not inconvenienced in any way by the
wind draught.

One shortcoming of such methods of arming an aeroplane will be observed.
Ahead firing only is possible; the weapon cannot be trained astern,
while similarly the line of fire on either broadside is severely
limited. This is one reason why the machine-gun armament of aerial craft
of the heavier-than-air type has not undergone extensive development.
In many instances the pilot and observer have expressed their preference
for repeating high velocity rifles over any form of fixed gun mounting,
and have recourse to the latter only when the conditions are extremely
favourable to its effective employment.

Efforts are now being made to equip the military type of aeroplane with
both forward and astern firing guns. The urgency of astern fire has
been brought home very vividly. Suppose, for instance, two hostile
aeroplanes, A and B, are in the air. A has t