bouring housewife looked in, and saw the bag bumping
about the ceiling, but rapidly losing its buoyancy as the smoke
escaped.

[Illustration: Montgolfier's Experimental Balloon.]

"Why not fasten a pan below the mouth of the bag," said she, "and
put your fire in that? Its weight will keep the bag upright, and
when it rises will carry the smoke and the pan up with it."

Acting upon the hint the brothers fixed up a small bag which sailed
up into the air beyond recapture. After various experiments a bag of
mixed paper and linen thirty-five feet in diameter was inflated and
released. It soared to a height of six thousand feet, and drifted
before the wind a mile or more before descending. The ascent took
place at Avonay, the home at the time of the Montgolfiers, and as
every sort of publicity was given in advance, a huge assemblage
including many officials of high estate gathered to witness it. A
roaring fire was built in a pit over the mouth of which eight men
held the great sack, which rolled, and beat about before the wind as
it filled and took the form of a huge ball. The crowd was
unbelieving and cynical, inclined to scoff at the idea that mere
smoke would carry so huge a construction up into the sky. But when
the signal was given to cast off, the balloon rose with a swiftness
and majesty that at first struck the crowd dumb, then moved it to
cheers of amazement and admiration. It went up six thousand feet and
the Montgolfiers were at once elevated to almost an equal height of
fame. The crowd which watched the experiment was wild with
enthusiasm; the Montgolfiers elated with the first considerable
victory over the force of gravity. They had demonstrated a principle
and made their names immortal. What remained was to develop that
principle and apply it to practical ends. That development, however,
proceeded for something more than a century before anything like a
practical airship was constructed.

But for the moment the attack on the forces which had kept the air
virgin territory to man was not allowed to lag. In Paris public
subscriptions were opened to defray the cost of a new and greater
balloon. By this time it was known that hydrogen gas, or
"inflammable air" as it was then called, was lighter than air. But
its manufacture was then expensive and public aid was needed for the
new experiment which would call at the outset for a thousand pounds
of iron filings and 498 pounds of sulphuric acid wherewith to
manufac