instruments. The Germans, with characteristic thoroughness, have
devoted considerable attention to this subject, but from the
results which they have achieved up to the present this guiding
knowledge appears to be more spectacular and impressive than
effective.

To put a captive balloon out of action one must either riddle the
envelope, causing it to leak like a sieve, blow the vessel to
pieces, or ignite the highly inflammable gas with which it is
inflated. Individual rifle fire will inflict no tangible damage.
A bullet, if it finds its billet, will merely pass through the
envelope and leave two small punctures. True, these vents will
allow the gas to escape, but this action will proceed so slowly
as to permit the vessel to remain aloft long enough to enable the
observer to complete his work. A lucky rifle volley, or the
stream of bullets from a machine gun may riddle the envelope,
precipitating a hurried descent, owing to the greater number of
perforations through which the gas is able to escape, but as a
rule the observer will be able to land safely.

Consequently the general practice is to shatter the aerostat, and
to this end either shrapnel, high explosive, or incendiary shells
will be used. The former must explode quite close to the balloon
in order to achieve the desired end, while the incendiary shell
must actually strike it, so as to fire the gas. The high
explosive shell may explode effectually some feet away from the
vessel, inasmuch as in this instance dependence is placed upon
the terrific concussion produced by the explosion which, acting
upon the fragile fabric of the balloon, brings about a complete
collapse of the envelope. If a shrapnel is well placed and