Where were they at that moment, 8 a.m. during that day called upon earth the sixth of December? Certainly in the neighbourhood of the moon, and even near enough for her to appear like a vast black screen upon the firmament. As to the distance which separated them, it was impossible to estimate it. The projectile, kept up by inexplicable forces, has grazed the north pole of the satellite at less than twenty-five miles' distance. But had that distance increased or diminished since they had been in the cone of shadow? There was no landmark by which to estimate either the direction or the velocity of the projectile. Perhaps it was going rapidly away from the disc and would soon leave the pure shadow. Perhaps, on the contrary, it was approaching it, and would before long strike against some elevated peak in the invisible atmosphere, which would have terminated the journey, doubtless to the detriment of the travellers. A discussion began upon this subject, and Michel Ardan, always rich in explanations, gave out the opinion that the bullet, restrained by lunar attraction, would end by falling on the moon like an aërolite on to the surface of the terrestrial globe. "In the first place," answered Barbicane, "all aërolites do not fall upon the surface of the earth; only a small proportion do so. Therefore, if we are aërolites it does not necessarily follow that we shall fall upon the moon." "Still," answered Michel, "if we get near enough--" "Error," replied Barbicane. "Have you not seen shooting stars by thousands in the sky at certain epochs?" "Yes." "Well, those stars, or rather corpuscles, only shine by rubbing against the atmospheric strata. Now, if they pass through the atmosphere, they pass at less than 16 miles from our globe, and yet they rarely fall. It is the same with our projectile. It may approach very near the moon, and yet not fall upon it." "But then," asked Michel, "I am curious to know how our vehicle would behave in space." "I only see two hypotheses," answered Barbicane, after some minutes' reflection. "What are they?" "The projectile has the choice between two mathematical curves, and it will follow the one or the other according to the velocity with which it is animated, and which I cannot now estimate." "Yes, it will either describe a parabola or an hyperbola." "Yes," answered Barbicane, "with some speed it will describe a parabola, and with greater speed an hyperbola." "I like those grand words!" exclaimed Michel Ardan. "I know at once what you mean. And what is your parabola, if you please?" "My friend," answered the captain, "a parabola is a conic section arising from cutting a cone by a plane parallel to one of its sides." "Oh!" said Michel in a satisfied tone. "It is about the same trajectory that the bomb of a howitzer describes." "Just so. And an hyperbola?" asked Michel.