ght be employed to
propel and direct a balloon. The immediate failure of all endeavours
of this sort, led them, still pursuing the analogy between a balloon
and a ship at sea, to try to navigate the air with sails. This again
proved futile. It is impossible for a balloon, or airship to "tack"
or manoeuvre in any way by sail power. It is in fact a monster sail
itself, needing some other power than the wind to make headway or
steerage way against the wind. The sail device was tested only to be
abandoned. Only when a trail rope dragging along the ground or sea
is employed does the sail offer sufficient resistance to the wind to
sway the balloon's course this way or that. And a trailer is
impracticable when navigating great heights.

[Illustration: Roberts Brothers' Dirigible.]

For these reasons the development of the balloon lagged, until Count
Zeppelin and M. Santos-Dumont consecrated their fortunes, their
inventive minds, and their amazing courage to the task of perfecting
a dirigible. In a book, necessarily packed with information
concerning the rapid development of aircraft which began in the last
decade of the nineteenth century and was enormously stimulated
during the war of all the world, the long series of early
experiments with balloons must be passed over hastily. Though
interesting historically these experiments were futile. Beyond
having discovered what could _not_ be done with a balloon the
practitioners of that form of aeronautics were little further along
in 1898 when Count Zeppelin came along with the first plan for a
rigid dirigible than they were when Blanchard in 1786, seizing a
favourable gale drifted across the English Channel to the French
shore, together with Dr. Jefferies, an American. It was just 124
years later that Bleriot, a Frenchman, made the crossing in an
airplane independently of favouring winds. It had taken a century
and a quarter to attain this independence.

In a vague way the earliest balloonists recognized that power,
independent of wind, was necessary to give balloons steerage way and
direction. Steam was in its infancy during the early days of
ballooning, but the efforts to devise some sort of an engine light
enough to be carried into the air were untiring. Within a year after
the experiments of the Montgolfier brothers, the suggestion was made
that the explosion of small quantities of gun-cotton and the
expulsion of the resulting gases might be utilized in some fashion
to ope