use?" someone asked. This plan was also tried, but was equally
unsuccessful.

Perhaps some of us may wonder how it is that a rudder is not as
serviceable on a balloon as it is on the stern of a boat. Have
you ever found yourself in a boat on a calm day, drifting idly
down stream, and going just as fast as the stream goes? Work the
rudder how you may, you will not alter the boat's course. But
supposing your boat moves faster than the stream, or by some
means or other is made to travel slower than the current, then
your rudder will act, and you may take what direction you will.

It was soon seen that if some method could be adopted whereby the
balloon moved through the air faster or slower than the wind,
then the aeronaut would be able to steer it. Nowadays a
balloon's pace can be accelerated by means of a powerful
motor-engine, but the invention of the petrol-engine is very
recent. Indeed, the cause of the long delay in the construction
of a steerable balloon was that a suitable engine could not be
found. A steam-engine, with a boiler of sufficient power to
propel a balloon, is so heavy that it would require a balloon of
impossible size to lift it.

One of the first serious attempts to steer a balloon by means of
engine power was that made by M. Giffard in 1852. Giffard's
balloon was about 100 feet long and 40 feet in diameter, and
resembled in shape an elongated cigar. A 3-horse-power
steam-engine, weighing nearly 500 pounds, was provided to work a
propeller, but the enormous weight was so great in proportion to
the lifting power of the balloon that for a time the aeronaut