nt, 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 balloo