"Upon your word of honour?"
"Yes."
"Then you are as clever as our president."
"No, Michel, all the difficulty consists in what Barbicane has done. It is to establish an equation which takes into account all the conditions of the problem. The rest is only a question of arithmetic, and requires nothing but a knowledge of the four rules."
"That's something," answered Michel Ardan, who had never been able to make a correct addition in his life, and who thus defined the rule: "A Chinese puzzle, by which you can obtain infinitely various results."
Still Barbicane answered that Nicholl would certainly have found the formula had he thought about it.
"I do not know if I should," said Nicholl, "for the more I study it the more marvellously correct I find it."
"Now listen," said Barbicane to his ignorant comrade, "and you will see that all these letters have a signification."
"I am listening," said Michel, looking resigned.
"d," said Barbicane, "is the distance from the centre of the earth to the centre of the moon, for we must take the centres to calculate the attraction."