framework, which was stayed with steel wire, maintained the shape
and rigidity of her gas-bags; hence vessels of this type are
known as RIGID air-ships. Externally the hull was covered with a
waterproof fabric.

Though, from outside, a rigid air-ship looks to be all in one
piece, within it is divided into numerous compartments. In
Zeppelin L1 there were eighteen separate compartments, each of
which contained a balloon filled with hydrogen gas. The object
of providing the vessel with these small balloons, or ballonets,
all separate from one another, was to prevent the gas collecting
all at one end of the ship as the vessel travelled through the
air. Outside the ballonets there was a ring-shaped, double
bottom, containing non-inflammable gas, and the whole was
enclosed in rubber-coated fabric.

The crew and motors were carried in cars slung fore and aft. The
ship was propelled by three engines, each of 170 horse-power.
One engine was placed in the forward car, and the two others in
the after car. To steer her to right or left, she had six
vertical planes somewhat resembling box-kites, while eight
horizontal planes enabled her to ascend or descend.

In Zeppelin L2, which was a later type of craft, there were four
motors capable of developing 820 horse-power. These drove four
propellers, which gave the craft a speed of about 45 miles an
hour.

The cars were connected by a gangway built within the framework.
On the top of the gas-chambers was a platform of aluminium alloy,