be from 70 to 80 miles per hour in the airship of the future, the
airship may be regarded as comparatively safe against attack from
the ordinary type of seaplane. The chief danger to be
apprehended is attack from small scouting seaplanes, possessing
great speed and the power to climb to a great height, or from
aeroplanes launched from the decks of ships. If, however, the
airship is fitted to carry several small scout aeroplanes of high
efficiency in the manner described in the previous chapter, it
will probably be able to defend itself sufficiently to enable it
to climb to a great height and thus make good its escape.

The airship, moreover, will be more or less immune from such
dangers if the non-inflamable gas, known as "C" gas, becomes
sufficiently cheap to be used for inflating airships. In the
past the expense of this gas has rendered its use absolutely
prohibitive, but it is believed that it can be produced in
the United States for such a figure as will make it compare
favourably with hydrogen.

The navigation of an airship during these long voyages proposed
will present no difficulty whatever. The airship, as opposed to
the aeroplane, is reasonably steady in the air and the ordinary
naval instruments can be used. In addition, "directional"
wireless telegraphy will prove of immense assistance. The method
at present in use is to call up simultaneously two land stations
which, knowing their own distance apart, and reading the
direction of the call, plot a triangle on a chart which fixes the
position of the airship. This position is then transmitted by
wireless to the airship. In the future the airship itself will
carry its own directional apparatus, with which it will be able