nd compact, is divided among four men, and carried in the manner of
knapsacks upon their backs. Although necessarily of limited radius,
such an installation is adequate for communication within the restricted
range of air-craft.

Greater difficulties have to be overcome in the mounting of a wireless
installation upon a dirigible. When the Zeppelin was finally accepted
by the German Government, the military authorities emphasised the great
part which wireless telegraphy was destined to play in connection with
such craft. But have these anticipations been fulfilled? By no means, as
a little reflection will suffice to prove.

In the first place, a wireless outfit is about the most dangerous piece
of equipment which could be carried by such a craft as the Zeppelin
unless it is exceptionally well protected. As is well known the rigidity
of this type of airship is dependent upon a large and complicated
network of aluminium, which constitutes the frame. Such a huge mass
of metal constitutes an excellent collector of electricity from the
atmosphere; it becomes charged to the maximum with electricity.

In this manner a formidable contributory source of danger to the airship
is formed. In fact, this was the reason why "Z-IV" vanished suddenly in
smoke and flame upon falling foul of the branches of trees during
its descent. At the time the Zeppelin was a highly charged electrical
machine or battery as it were, insulated by the surrounding air.
Directly the airship touched the trees a short circuit was established,
and the resultant spark sufficed to fire the gas, which is continuously
exuding from the gas bags.

After this accident minute calculations were made and it was ascertained
that a potential difference of no less than 100,00 volts existed between
the framework of the dirigible and the trees. This tension sufficed
to produce a spark 4 inches in length. It is not surprising that the
establishment of the electric equilibrium by contact with the trees,
which produced such a spark should fire the hydrogen inflation charge.
In fact the heat generated was so intense that the aluminium metallic
framework was fused. The measurements which were made proved that the
gas was consumed within 15 seconds and the envelope destroyed within 20
seconds.

As a result of this disaster endeavours were made to persuade Count
Zeppelin to abandon the use of aluminium for the framework of his
balloon but they were fruitless, a result no doubt