"For the reason that 'he is always brave who never suspects danger.' I know nothing, it is true; but it is precisely my very weakness which constitutes my strength." "Your weakness amounts to folly," retorted the unknown in a passion. "All the better," replied our Frenchman, "if it carries me up to the _moon._" Barbicane and his colleagues devoured with their eyes the intruder who had so boldly placed himself in antagonism to their enterprise. Nobody knew him, and the president, uneasy as to the result of so free a discussion, watched his new friend with some anxiety. The meeting began to be somewhat fidgety also, for the contest directed their attention to the dangers, if not the actual impossibilities, of the proposed expedition. Illustration: ATTACK AND RIPOSTE. "Sir," replied Ardan's antagonist, "there are many and incontrovertible reasons which prove the absence of an atmosphere in the moon. I might say that, _à priori_, if one ever did exist, it must have been absorbed by the earth; but I prefer to bring forward indisputable facts." "Bring them forward then, sir, as many as you please." "You know," said the stranger, "that when any luminous rays cross a medium such as the air, they are deflected out of the straight line; in other words, they undergo _refraction._ Well! When stars are occulted by the moon, their rays, on grazing the edge of her disc, exhibit not the least deviation, nor offer the slightest indication of refraction. It follows, therefore, that the moon cannot be surrounded by an atmosphere." "In point of fact," replied Ardan, "this is your chief, if not your _only_ argument; and a really scientific man might be puzzled to answer it. For myself, I will simply say that it is defective, because it assumes that the angular diameter of the moon has been completely determined, which is not the case. But let us proceed. Tell me, my dear sir, do you admit the existence of volcanoes on the moon's surface?" "_Extinct_, yes! In activity, no!" "These volcanoes, however, were at one time in a state of activity?" "True! but, as they furnished themselves the oxygen necessary for combustion, the mere fact of their eruption does not prove the presence of an atmosphere." "Proceed again, then; and let us set aside this class of arguments in order to come to direct observations. In 1715 the astronomers Louville and Halley, watching the eclipse of the 3rd May, remarked some very extraordinary scintillations. These jets of light, rapid in nature, and of frequent recurrence, they attributed to thunderstorms generated in the lunar atmosphere." "In 1715," replied the unknown, "the astronomers Louville and Halley mistook for lunar phenomena some which were purely terrestrial, such as meteoric or other bodies which are generated in our own atmosphere. This was the scientific explanation at the time of the facts; and that is my answer now."