the very spot where the aeronef had landed for a few hours.

Her ascensional power was due to the very lightest of gaseous bodies.
Ordinary lighting gas possesses an elevating force of about 700 grams
for every cubic meter. But hydrogen possesses an ascensional force
estimated at 1,100 grams per cubic meter. Pure hydrogen prepared
according to the method of the celebrated Henry Gifford filled the
enormous balloon. And as the capacity of the "Go-Ahead" was 40,000
cubic meters, the ascensional power of the gas she contained was
40,000 multiplied by 1,100 or 44,000 kilograms.

On this 29th of April everything was ready. Since eleven o'clock the
enormous aerostat had been floating a few feet from the ground ready
to rise in mid-air. It was splendid weather and seemed to have been
made specially for the experiment, although if the breeze had been
stronger the results might have been more conclusive. There had never
been any doubt that a balloon could be guided in a calm atmosphere;
but to guide it when the atmosphere is in motion is quite another
thing; and it is under such circumstances that the experiment should
be tried.

But there was no wind today, nor any sign of any. Strange to say,
North America on that day omitted to send on to Europe one of those
first-class storms which it seems to have in such inexhaustible
numbers. A better day could not have been chosen for an aeronautic
experiment.

The crowd was immense in Fairmount Park; trains had poured into the
Pennsylvania capital sightseers from the neighboring states;
industrial and commercial life came to a standstill that the people