tructed a
steam engine of 5 horsepower with a weight of only 100 lbs.--a great
achievement for his day. Having got his engine, he set about making the
balloon which it was to drive; this he built with the aid of two other
enthusiasts, diverging from Meusnier's ideas by making the ends pointed,
and keeping the body narrowed from Meusnier's ellipse to a shape more
resembling a rather fat cigar. The length was 144 feet, and the greatest
diameter only 40 feet, while the capacity was 88,000 cubic feet. A net
which covered the envelope of the balloon supported a spar, 66 feet in
length, at the end of which a triangular sail was placed vertically to
act as rudder. The car, slung 20 feet below the spar, carried the engine
and propeller. Engine and boiler together weighed 350 lbs., and drove
the 11 foot propeller at 110 revolutions per minute.

As precaution against explosion, Giffard arranged wire gauze in front
of the stoke-hole of his boiler, and provided an exhaust pipe which
discharged the waste gases from the engine in a downward direction. With
this first dirigible he attained to a speed of between 6 and 8 feet per
second, thus proving that the propulsion of a balloon was a possibility,
now that steam had come to supplement human effort.

Three years later he built a second dirigible, reducing the diameter and
increasing the length of the gas envelope, with a view to reducing air
resistance. The length of this was 230 feet, the diameter only 33 feet,
and the capacity was 113,000 cubic feet, while the upper part of the
envelope, to which the covering net was attached, was specially covered
to ensure a stiffening effect. The car of this dirigible was dropped
rather lower than that of the first machine, in order to provide more
thoroughly against the danger of explosions. Giffard, with a companion
named Yon as passenger, took a trial trip on this vessel, and made a
journey against the wind, though slowly. In commencing to descend, the
nose of the envelope tilted upwards, and the weight of the car and
its contents caused the net to slip, so that just before the dirigible
reached the ground, the envelope burst. Both Giffard and his companion
escaped with very slight injuries.

Plans were immediately made for the construction of a third dirigible,
which was to be 1,970 feet in length, 98 feet in extreme diameter, and
to have a capacity of 7,800,000 cubic feet of gas. The engine of this
giant was to have weighed 30 tons, and w