When petrol engines became available, they gave an impetus to the building of airships; for, like the aeroplane, the airship needed a motive agent which gives a high power for a low weight. One of the first to use a petrol motor in an airship with success was M. Santos-Dumont, whose name has been mentioned in connection with aeroplanes. He tested small, light airships, driven by petrol engines and two-bladed propellers—as illustrated in figure; and with one of these, on a calm, still day, he flew over Paris and round the Eiffel Tower.

A. Gas envelope
B. Wheeled framework which carried motor, propeller, and pilot’s seat
C. Elevating-plane
D. Horizontal rear-plane
E. Rudder.