for navigating the ship and also provides a housing for the
engines. In the early days swivelling propellers were considered
a great adjunct, as with their upward and downward thrust they
proved of great value in landing. Nowadays, owing to greater
experience, landing does not possess the same difficulty as in
the past, and swivelling propellers have been abandoned except in
rigid airships, and even in the later types of these they have
been dispensed with.

Owing to the great range of an airship a thoroughly reliable
engine is a paramount necessity. The main requirements
are--firstly, that it must be capable of running for long periods
without a breakdown; secondly, that it must be so arranged that
minor repairs can be effected in the air; and thirdly, that
economy of oil and fuel is of far greater importance to an
airship than the initial weight of the engine itself.


HANDLING AND FLYING OF AIRSHIPS

The arrangements made for handling airships on the ground and
while landing, and also for moving them in the open, provide
scope for great ingenuity. An airship when about to land is
brought over the aerodrome and is "ballasted up" so that she
becomes considerably lighter than the air which she displaces.
The handling party needs considerable training, as in gusty
weather the safety of the ship depends to a great extent upon its
skill in handling her. The ship approaches the handling party
head to wind and the trail rope is dropped; it is taken by the
handling party and led through a block secured to the ground and