"I am going to tell you," replied Barbicane quietly.

"Nothing is more easy than to reduce this mass to one quarter of
its bulk. You know that curious cellular matter which
constitutes the elementary tissues of vegetable? This substance
is found quite pure in many bodies, especially in cotton, which
is nothing more than the down of the seeds of the cotton plant.
Now cotton, combined with cold nitric acid, become transformed
into a substance eminently insoluble, combustible, and explosive.
It was first discovered in 1832, by Braconnot, a French chemist,
who called it xyloidine. In 1838 another Frenchman, Pelouze,
investigated its different properties, and finally, in 1846,
Schonbein, professor of chemistry at Bale, proposed its employment
for purposes of war. This powder, now called pyroxyle, or
fulminating cotton, is prepared with great facility by simply
plunging cotton for fifteen minutes in nitric acid, then washing
it in water, then drying it, and it is ready for use."

"Nothing could be more simple," said Morgan.

"Moreover, pyroxyle is unaltered by moisture-- a valuable
property to us, inasmuch as it would take several days to charge
the cannon. It ignites at 170 degrees in place of 240, and its
combustion is so rapid that one may set light to it on the top
of the ordinary powder, without the latter having time to ignite."

"Perfect!" exclaimed the major.

"Only it is more expensive."