Barbicane had no means of estimating the projectile’s speed, but reasoning showed that it must uniformly decrease, according to the laws of mechanical reasoning. Having admitted that the projectile was describing an orbit around the moon, this orbit must necessarily be elliptical; science proves that it must be so. No motive body circulating round an attracting body fails in this law. Every orbit described in space is elliptical. And why should the projectile of the Gun Club escape this natural arrangement? In elliptical orbits, the attracting body always occupies one of the foci; so that at one moment the satellite is nearer, and at another farther from the orb around which it gravitates. When the earth is nearest the sun she is in her perihelion; and in her aphelion at the farthest point. Speaking of the moon, she is nearest to the earth in her perigee, and farthest from it in her apogee. To use analogous expressions, with which the astronomers’ language is enriched, if the projectile remains as a satellite of the moon, we must say that it is in its “aposelene” at its farthest point, and in its “periselene” at its nearest. In the latter case, the projectile would attain its maximum of speed; and in the former its minimum. It was evidently moving toward its aposelenitical point; and Barbicane had reason to think that its speed would decrease up to this point, and then increase by degrees as it neared the moon. This speed would even become nil, if this point joined that of equal attraction. Barbicane studied the consequences of these different situations, and thinking what inference he could draw from them, when he was roughly disturbed by a cry from Michel Ardan.
“By Jove!” he exclaimed, “I must admit we are down-right simpletons!”
“I do not say we are not,” replied Barbicane; “but why?”
“Because we have a very simple means of checking this speed which is bearing us from the moon, and we do not use it!”
“And what is the means?”
“To use the recoil contained in our rockets.”
“Done!” said Nicholl.
“We have not used this force yet,” said Barbicane, “it is true, but we will do so.”
“When?” asked Michel.
“When the time comes. Observe, my friends, that in the position occupied by the projectile, an oblique position with regard to the lunar disc, our rockets, in slightly altering its direction, might turn it from the moon instead of drawing it nearer?”