ith it Giffard expected to
attain a speed of 40 miles per hour. Cost prevented the scheme being
carried out, and Giffard went on designing small steam engines until his
invention of the steam injector gave him the funds to turn to dirigibles
again. He built a captive balloon for the great exhibition in London
in 1868, at a cost of nearly L30,000, and designed a dirigible balloon
which was to have held a million and three quarters cubic feet of gas,
carry two boilers, and cost about L40,000. The plans were thoroughly
worked out, down to the last detail, but the dirigible was never
constructed. Giffard went blind, and died in 1882--he stands as the
great pioneer of dirigible construction, more on the strength of the
two vessels which he actually built than on that of the ambitious later
conceptions of his brain.

In 1872 Dupuy de Lome, commissioned by the French government, built a
dirigible which he proposed to drive by man-power--it was anticipated
that the vessel would be of use in the siege of Paris, but it was not
actually tested till after the conclusion of the war. The length of
this vessel was 118 feet, its greatest diameter 49 feet, the ends being
pointed, and the motive power was by a propeller which was revolved by
the efforts of eight men. The vessel attained to about the same speed as
Giffard's steam-driven airship; it was capable of carrying fourteen
men, who, apart from these engaged in driving the propeller, had to
manipulate the pumps which controlled the air bags inside the gas
envelope.

In the same year Paul Haenlein, working in Vienna, produced an airship
which was a direct forerunner of the Lebaudy type, 164 feet in length,
30 feet greatest diameter, and with a cubic capacity of 85,000 feet.
Semi-rigidity was attained by placing the car as close to the envelope
as possible, suspending it by crossed ropes, and the motive power was
a gas engine of the Lenoir type, having four horizontal cylinders, and
giving about 5 horse-power with a consumption of about 250 cubic feet
of gas per hour. This gas was sucked from the envelope of the balloon,
which was kept fully inflated by pumping in compensating air to the air
bags inside the main envelope. A propeller, 15 feet in diameter, was
driven by the Lenoir engine at 40 revolutions per minute. This was the
first instance of the use of an internal combustion engine in connection
with aeronautical experiments.

The envelope of this dirigible was rendered airti