"Then," said Michel Ardan, in his sly tone,"mathematics have not said their last word?"
"Certainly not," replied Barbicane.
"Well, perhaps the Selenites have carried the integral calculus farther than you have; and, by the bye, what is this 'integral calculus?'"
"It is a calculation the converse of the differential," replied Barbicane seriously.
"Much obliged; it is all very clear, no doubt."
"And now," continued Barbicane, "a slip of paper and a bit of pencil, and before a half-hour is over I will have found the required formula."