“Unless you prefer gold-powder,” replied the major, laughing, which provoked a threatening gesture from the steel hook of his susceptible friend.

Until then Barbicane had kept himself aloof from the discussion; he listened, and had evidently an idea.  He contented himself with saying simply—­

“Now, my friends, what quantity of powder do you propose?”

The three members of the Gun Club looked at one another for the space of a minute.

“Two hundred thousand pounds,” said Morgan at last.

“Five hundred thousand,” replied the major.

“Eight hundred thousand,” exclaimed J.T.  Maston.

This, time Elphinstone dared not tax his colleague with exaggeration.  In fact, the question was that of sending to the moon a projectile weighing 20,000 lbs., and of giving it an initial force of 2000 yards a second.  A moment of silence, therefore, followed the triple proposition made by the three colleagues.

It was at last broken by President Barbicane.

“My brave comrades,” said he in a quiet tone, “I start from this principle, that the resistance of our cannon, in the given conditions, is unlimited.  I shall, therefore, surprise the Honourable J.T.  Maston when I tell him that he has been timid in his calculations, and I propose to double his 800,000 lbs. of powder.”

“Sixteen hundred thousand pounds!” shouted J.T.  Maston, jumping out of his chair.

“Quite as much as that.”

“Then we shall have to come back to my cannon half a mile long.”

“It is evident,” said the major.

“Sixteen hundred thousand pounds of powder,” resumed the Secretary of Committee, “will occupy about a space of 22,000 cubic feet; now, as your cannon will only hold about 54,000 cubic feet, it will be half full, and the chamber will not be long enough to allow the explosion of the gas to give sufficient impulsion to your projectile.”

There was nothing to answer.  J.T.  Maston spoke the truth.  They all looked at Barbicane.

“However,” resumed the president, “I hold to that quantity of powder.  Think! 1,600,000 pounds of powder will give 6,000,000,000 litres of gas.”

“Then how is it to be done?” asked the general.

“It is very simple.  We must reduce this enormous quantity of powder, keeping at the same time its mechanical power.”

“Good!  By what means?”

“I will tell you,” answered Barbicane simply.

His interlocutors all looked at him.

“Nothing is easier, in fact,” he resumed, “than to bring that mass of powder to a volume four times less.  You all know that curious cellular matter which constitutes the elementary tissues of vegetables?”

“Ah!” said the major, “I understand you, Barbicane.”