"Well, these shooting stars," continued Barbican, "or rather these wandering particles of matter, shine only from being inflamed by the friction of the atmosphere. Therefore they can never be at a greater distance from the Earth than 30 or 40 miles at furthest, and yet they seldom fall on it. So with our Projectile. It may go very close to the Moon without falling into it." "But our roving Projectile must pull up somewhere in the long run," replied Ardan, "and I should like to know where that somewhere can be, if not in the Moon." "Softly again, dear boy," said Barbican; "how do you know that our Projectile must pull up somewhere?" "It's self-evident," replied Ardan; "it can't keep moving for ever." "Whether it can or it can't depends altogether on which one of two mathematical curves it has followed in describing its course. According to the velocity with which it was endowed at a certain moment, it must follow either the one or the other; but this velocity I do not consider myself just now able to calculate." "Exactly so," chimed in M'Nicholl; "it must describe and keep on describing either a parabola or a hyperbola." "Precisely," said Barbican; "at a certain velocity it would take a parabolic curve; with a velocity considerably greater it should describe a hyperbolic curve." "I always did like nice corpulent words," said Ardan, trying to laugh; "bloated and unwieldy, they express in a neat handy way exactly what you mean. Of course, I know all about the high--high--those high curves, and those low curves. No matter. Explain them to me all the same. Consider me most deplorably ignorant on the nature of these curves." "Well," said the Captain, a little bumptiously, "a parabola is a curve of the second order, formed by the intersection of a cone by a plane parallel to one of its sides." "You don't say so!" cried Ardan, with mouth agape. "Do tell!" "It is pretty nearly the path taken by a shell shot from a mortar." "Well now!" observed Ardan, apparently much surprised; "who'd have thought it? Now for the high--high--bully old curve!" "The hyperbola," continued the Captain, not minding Ardan's antics, "the hyperbola is a curve of the second order, formed from the intersection of a cone by a plane parallel to its axis, or rather parallel to its two _generatrices_, constituting two separate branches, extending indefinitely in both directions." "Oh, what an accomplished scientist I'm going to turn out, if only left long enough at your feet, illustrious _maestro_!" cried Ardan, with effusion. "Only figure it to yourselves, boys; before the Captain's lucid explanations, I fully expected to hear something about the high curves and the low curves in the back of an Ancient Thomas! Oh, Michael, Michael, why didn't you know the Captain earlier?"