in gradually breaking up and destroying this Armada of the Air;
and the Zeppelin was forced back to the one line of work in which
it has proved a success, viz., scouting for the German fleet in
the few timid sallies it has made from home ports.



CHAPTER XI
The Semi-rigid Air-ship

Modern air-ships are of three general types: RIGID, SEMI-RIGID,
and NON-RIGID. These differ from one another, as the names
suggest, in the important feature, the RIGIDITY, NON-RIGIDITY,
and PARTIAL RIGIDITY of the gas envelope.

Hitherto we have discussed the RIGID type of vessel with which
the name of Count Zeppelin is so closely associated. This vessel
is, as we have seen, not dependent for its form on the gas-bag,
but is maintained in permanent shape by means of an aluminium
framework. A serious disadvantage to this type of craft is that
it lacks the portability necessary for military purposes. It is
true that the vessel can be taken to pieces, but not quickly.
The NON-RIGID type, on the other hand, can be quickly deflated,
and the parts of the car and engine can be readily transported to
the nearest balloon station when occasion requires.

In the SEMI-RIGID type of air-ship the vessel is dependent for
its form partly on its framework and partly on the form of the
gas envelope. The under side of the balloon consists of a flat
rigid framework, to which the planes are attached, and from which