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 furnish 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 of 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."

"On again, then," replied Ardan; "Herschel, in 1787, observed a great number of luminous points on the moon's surface, did he not?"

"Yes! but without offering any solution of them. Herschel himself never inferred from them the necessity of a lunar atmosphere. And I may add that Baeer and Maedler, the two great authorities upon the moon, are quite agreed as to the entire absence of air on its surface."

A movement was here manifest among the assemblage, who appeared to be growing excited by the arguments of this singular personage.

"Let us proceed," replied Ardan, with perfect coolness, "and come to one important fact. A skillful French astronomer, M. Laussedat, in watching the eclipse of July 18, 1860, probed that the horns of the lunar crescent were rounded and truncated. Now, this appearance could only have been produced by a deviation of the solar rays in traversing the atmosphere of the moon. There is no other possible explanation of the facts."

"But is this established as a fact?"

"Absolutely certain!"

A counter-movement here took place in favor of the hero of the meeting, whose opponent was now reduced to silence. Ardan resumed the conversation; and without exhibiting any exultation at the advantage he had gained, simply said:

"You see, then, my dear sir, we must not pronounce with absolute positiveness against the existence of an atmosphere in the moon. That atmosphere is, probably, of extreme rarity; nevertheless at the present day science generally admits that it exists."

"Not in the mountains, at all events," returned the unknown, unwilling to give in.

"No! but at the bottom of the valleys, and not exceeding a few hundred feet in height."

"In any case you will do well to take every precaution, for the air will be terribly rarified."

"My good sir, there will always be enough for a solitary individual; besides, once arrived up there, I shall do my best to economize, and not to breathe except on grand occasions!"

A tremendous roar of laughter rang in the ears of the mysterious interlocutor, who glared fiercely round upon the assembly.

"Then," continued Ardan, with a careless air, "since we are in accord regarding the presence of a certain atmosphere, we are forced to admit the presence of a certain quantity of water. This is a happy consequence for me. Moreover, my amiable contradictor, permit me to submit to you one further observation. We only know one side of the moon's disc; and if there is but little air on the face presented to us, it is possible that there is plenty on the one turned away from us."

"And for what reason?"

"Because the moon, under the action of the earth's attraction, has assumed the form of an egg, which we look at from the smaller end.