f the kind of gas used by that
experimenter to inflate his balloon. By one of the frequent coincidences
in the history of the sciences, hydrogen gas had been discovered six
years previously by the great English physician Cavendish, and it had
hardly even been tested in the laboratories of the chemists when it all
at once became famous. A young man well versed in physics, Professor
Charles, assisted by two practical men, the brothers Robert, threw
himself ardently into the investigation of the modes of inflating
balloons with this gas, which was then called INFLAMMABLE AIR. Guessing
that it was much lighter than that which Montgolfier had been obliged to
make use of in his third-rate provincial town, Charles leagued himself
with his two assistants to constrict a balloon of taffeta, twelve feet
in diameter, covered with india-rubber, and to inflate it with hydrogen.

The thing thus arranged, a subscription was opened. The projected
experiment having been talked of all over Paris, every one was struck
with the idea, and subscriptions poured in. Even the most illustrious
names are to be found in the list, which may be called the first
national subscription in France. Nothing had been written of the
forthcoming event in any public paper, yet all Paris seemed to flock to
contribute to the curious experiment.

The inflation with hydrogen was effected in a very curious manner. As
much as 1,125 lbs. of iron and 560 lbs. of sulphuric acid were found
necessary to inflate a balloon which had scarcely a lifting power of
22 lbs., and the process of filling took no less than four hours. At
length, however, at the end of the fourth hour, the balloon, composed of
strips of silk, coated with varnish, floated, two-thirds full, from the
workshop of the brothers Robert.

On the morning of the 26th of August, the day before the ascent was
to be made, the balloon was visited at daybreak, and found to be in
a promising state. At two o'clock on the following morning its
constructors began to make preparations to transport it to the Champ
de Mars, from which place it was to be let loose. Skilled workmen were
employed in its removal, and every precaution was taken that the gas
with which it was charged should not be allowed to escape. In the
meantime the excitement of the people about this wonderful structure
was rising to the highest pitch. The wagon on which it was placed
for removal was surrounded on all sides by eager multitudes, and the
n