But why was there no wind to assist at this magnificent experiment?
It was regrettable. Doubtless the spectators would have seen the
"Go-Ahead" unhesitatingly execute all the movements of a
sailing-vessel in beating to windward, or of a steamer driving in the
wind's eye.

At this moment the aerostat rose a few hundred yards. The maneuver
was understood below. Uncle Prudent and his companions were going in
search of a breeze in the higher zones, so as to complete the
experiment. The system of cellular balloons--analogous to the
swimming bladder in fishes--into which could be introduced a certain
amount of air by pumping, had provided for this vertical motion.
Without throwing out ballast or losing gas the aeronaut was able to
rise or sink at his will. Of course there was a valve in the upper
hemisphere which would permit of a rapid descent if found necessary.
All these contrivances are well known, but they were here fitted in
perfection.

The "Go-Ahead" then rose vertically. Her enormous dimensions
gradually grew smaller to the eye, and the necks of the crowd were
almost cricked as they gazed into the air. Gradually the whale became
a porpoise, and the porpoise became a gudgeon. The ascensional
movement did not cease until the "Go-Ahead" had reached a height of
fourteen thousand feet. But the air was so free from mist that she
remained clearly visible.

However, she remained over the clearing as if she were a fixture. An
immense bell had imprisoned the atmosphere and deprived it of
movement; not a breath of wind was there, high or low. The aerostat
maneuvered without encountering any resistance, seeming very small