ot under
conditions that made it a matter of scientific record.

But setting aside for the time the work done by Santos-Dumont with
machines heavier than air, let us consider his triumphs with
balloons at the opening of his career. He had come to France about
forty years after Henry Giffard had demonstrated the practicability
of navigating a balloon 144 feet long and 34 feet in diameter with a
three-horse-power steam-engine. But no material success attended
this demonstration, important as it was, and the inventor turned his
attention to captive balloons, operating one at the Paris Exposition
of 1878 that took up forty passengers at a time. There followed
Captain Renard to whose achievement we have already referred. He had
laid down as the fundamentals of a dirigible balloon these
specifications:

A cigar, or fishlike shape.

An internal sack or ballonet into which air might be pumped to
replace any lost gas, and maintain the shape of the balloon.

A keel, or other longitudinal brace, to maintain the longitudinal
stability of the balloon and from which the car containing the
motor might be hung.

A propeller driven by a motor, the size and power of both to be
as great as permitted by the lifting power of the balloon.

A rudder capable of controlling the course of the ship.

Santos-Dumont adopted all of these specifications, but added to them
certain improvements which gave his airships--he built five of them
before taking his first prize--notable superiority over that of
Renard. To begin with he had the inestimable advantage of having the
gasoline motor. He further lightened his craft by having the
envelope made of Japanese silk, in flat defiance of all the builders
of balloons who assured him that the substance was too light and its
use would be suicidal. "All right," said the innovator to his
favourite constructor, who refused to build him a balloon of that
material, "I'll build it myself." In the face of this threat the
builder capitulated. The balloon was built, and the silk proved to
be the best fabric available at that time for the purpose. A keel
made of strips of pine banded together with aluminum wire formed the
backbone of the Santos-Dumont craft, and from it depended the car
about one quarter of the length of the balloon and hung squarely
amidships. The idea of this keel occurred to the inventor while
pleasuring at Nice. Later it saved his life.

One nov