In this early work we see the ingredients of Verne's later _Voyages
Extraordinaires_; characters brought or thrown together on a journey to
afar; introduction of new characters part way through the story; careful
scientific explanation of critical events (the ascension, filling
the balloon, rising and falling, ballast); use of dialogue to convey
scientific information (the history of ballooning); use of scientific
instruments (barometer, compass); chapter heads to presage the
story; escapes from perilous events caused by scientific or natural
catastrophes.

One may also wonder why Hetzel removed the description of the inflation
of the balloon with hydrogen gas. In fact hydrogen is barely mentioned
in the revised story. Could it be that while Hetzel approved of Verne's
scientific descriptions of impossible undertakings, when it came to real
exploits such as ballooning he did not want his juvenile readers
experimenting with the "hogsheads of sulphuric acid and nails" to
produce explosive hydrogen? In fact in the Hetzel version the lifting
gas hydrogen is replaced with "illuminating gas", an inferior, though
lighter than air material, but one which his readers would find
difficult to use for deadly experimentation.

It may also be that Verne had little to do with this volume; Hetzel may
have edited the collection so that it would count as one of the required
volumes Verne was to produce annually. The correspondence archives may
shed some light.

Ms. Wilbur also translated other articles on ballooning from the French.
It is also interesting that she retained in her translation the original
units which Verne used (metre, feet, leagues), a practice forgotten