n 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 des