when it is tilted.

In the picture there is shown the petrol storage-tank, which is
suspended immediately under the rear horizontal plane, where it
is out of danger of ignition from the hot engine placed in the
car.



CHAPTER XII
A Non-rigid Balloon

Hitherto we have described the rigid and semi-rigid types of
air-ships. We have seen that the former maintains its shape
without assistance from the gas which inflates its envelope and
supplies the lifting power, while the latter, as its name
implies, is dependent for its form partly on the flat rigid
framework to which the car is attached, and partly on the gas
balloon.

We have now to turn our attention to that type of craft known as
a NON-RIGID BALLOON. This vessel relies for its form ENTIRELY
upon the pressure of the gas, which keeps the envelope distended
with sufficient tautness to enable it to be driven through the
air at a considerable speed.

It will at once be seen that the safety of a vessel of this type
depends on the maintenance of the gas pressure, and that it is
liable to be quickly put out of action if the envelope becomes
torn. Such an occurrence is quite possible in war. A