“Perfect,” said Michel.

“And g, the gravity, is to Florida 9-1/81 metres.  From whence it results that gr equals—­”

“Sixty-two million four hundred and twenty-six thousand square metres,” answered Nicholl.

“What next?” asked Michel Ardan.

“Now that the expressions are reduced to figures, I am going to find the velocity v zero—­that is to say, the velocity that the projectile ought to have on leaving the atmosphere to reach the point of equal attraction with no velocity.  The velocity at that point I make equal zero, and x, the distance where the neutral point is, will be represented by the nine-tenths of d—­that is to say, the distance that separates the two centres.”

“I have some vague idea that it ought to be so,” said Michel.

“I shall then have, x equals nine-tenths of d, and v equals zero, and my formula will become—­”

Barbicane wrote rapidly on the paper—­

     2 10r 1 10r r
    v = 2 gr { 1 — —–­ —–­ ( —–­ — —–­) }
     0 9d 81 d d-r

Nicholl read it quickly.

“That’s it! that is it!” he cried.

“Is it clear?” asked Barbicane.

“It is written in letters of fire!” answered Nicholl.

“Clever fellows!” murmured Michel.

“Do you understand now?” asked Barbicane.

“If I understand!” cried Michel Ardan.  “My head is bursting with it.”

“Thus,” resumed Barbicane, “v zero square equals 2 gr multiplied by 1 minus 10 r upon 9 d minus 1/81 multiplied by 10 r upon d minus r upon d minus r.”

“And now,” said Nicholl, “in order to obtain the velocity of the bullet as it emerges from the atmosphere I have only to calculate.”

The captain, like a man used to overcome all difficulties, began to calculate with frightful rapidity.  Divisions and multiplications grew under his fingers.  Figures dotted the page.  Barbicane followed him with his eyes, whilst Michel Ardan compressed a coming headache with his two hands.

“Well, what do you make it?” asked Barbicane after several minutes’ silence.

“I make it 11,051 metres in the first second.”

“What do you say?” said Barbicane, starting.

“Eleven thousand and fifty-one metres.”

“Malediction!” cried the president with a gesture of despair.

“What’s the matter with you?” asked Michel Ardan, much surprised.

“The matter! why if at this moment the velocity was already diminished one-third by friction, the initial speed ought to have been—­”

“Sixteen thousand five hundred and seventy-six metres!” answered Nicholl.

“But the Cambridge Observatory declared that 11,000 metres were enough at departure, and our bullet started with that velocity only!”