the level of
London, where he began his ascent--to 29 degrees at the maximum
height reached. He took up an electrometer, a hydrometer, a compass, a
thermometer, and a Toricelli barometer, together with bottles of water,
in order to collect samples of the air at different heights. In 1785 he
made a second ascent, when trigonometrical observations of the height of
the balloon were made from the French coast, giving an altitude of 4,800
feet.

The matter was taken up on its scientific side very early in America,
experiments in Philadelphia being almost simultaneous with those of the
Montgolfiers in France. The flight of Rozier and d'Arlandes inspired two
members of the Philadelphia Philosophical Academy to construct a balloon
or series of balloons of their own design; they made a machine which
consisted of no less than 47 small hydrogen balloons attached to a
wicker car, and made certain preliminary trials, using animals as
passengers. This was followed by a captive ascent with a man as
passenger, and eventually by the first free ascent in America, which
was undertaken by one James Wilcox, a carpenter, on December 28th,
1783. Wilcox, fearful of falling into a river, attempted to regulate his
landing by cutting slits in some of the supporting balloons, which was
the method adopted for regulating ascent or descent in this machine.
He first cut three, and then, finding that the effect produced was not
sufficient, cut three more, and then another five--eleven out of the
forty-seven. The result was so swift a descent that he dislocated his
wrist on landing.

A NOTE ON BALLONETS OR AIR BAGS.

Meusnier, toward the end of the eighteenth century, was first to
conceive the idea of compensating for the loss of gas due to expansion
by fitting to the interior of a free balloon a ballonet, or air bag,
which could be pumped full of air so as to retain the shape and rigidity
of the envelope.

The ballonet became particularly valuable as soon as airship
construction became general, and it was in the course of advance
in Astra Torres design that the project was introduced of using the
ballonets in order to give inclination from the horizontal. In the
earlier Astra Torres, trimming was accomplished by moving the car fore
and aft--this in itself was an advance on the separate 'sliding weigh'
principle--and this was the method followed in the Astra Torres bought
by the British Government from France in 1912 for training airshi