paper, "you have worked the thing out very well. You have the integral
equation of the living forces, and I have no doubt it will give us the
result sought for."

"Yes, but I should like to understand it, you know," cried Ardan: "I
would give ten years of the Captain's life to understand it!"

"Listen then," said Barbican. "Half of _v_ prime squared less _v_
squared, is the formula giving us the half variation of the living
force."

"Mac pretends he understands all that!"

"You need not be a _Solomon_ to do it," said the Captain. "All these
signs that you appear to consider so cabalistic form a language the
clearest, the shortest, and the most logical, for all those who can read
it."

"You pretend, Captain, that, by means of these hieroglyphics, far more
incomprehensible than the sacred Ibis of the Egyptians, you can
discover the velocity at which the Projectile should start?"

"Most undoubtedly," replied the Captain, "and, by the same formula I can
even tell you the rate of our velocity at any particular point of our
journey."

"You can?"

"I can."