"How fortunate to have such a handy thing as an atmosphere around us,"

cried the Frenchman; "it not only enables us to breathe, but it actually keeps us from sizzling up like griskins."

"Yes," said the Captain, "but unfortunately we can't say so much for the Moon."

"Oh pshaw!" cried Ardan, always full of confidence. "It's all right there too! The Moon is either inhabited or she is not. If she is, the inhabitants must breathe. If she is not, there must be oxygen enough left for we, us and co., even if we should have to go after it to the bottom of the ravines, where, by its gravity, it must have acc.u.mulated!

So much the better! we shall not have to climb those thundering mountains!"

So saying, he jumped up and began to gaze with considerable interest on the lunar disc, which just then was glittering with dazzling brightness.

"By Jove!" he exclaimed at length; "it must be pretty hot up there!"

"I should think so," observed the Captain; "especially when you remember that the day up there lasts 360 hours!"

"Yes," observed Barbican, "but remember on the other hand that the nights are just as long, and, as the heat escapes by radiation, the mean temperature cannot be much greater than that of interplanetary s.p.a.ce."

"A high old place for living in!" cried Ardan. "No matter! I wish we were there now! Wouldn't it be jolly, dear boys, to have old Mother Earth for our Moon, to see her always on our sky, never rising, never setting, never undergoing any change except from New Earth to Last Quarter! Would not it be fun to trace the shape of our great Oceans and Continents, and to say: 'there is the Mediterranean! there is China!

there is the gulf of Mexico! there is the white line of the Rocky Mountains where old Marston is watching for us with his big telescope!'

Then we should see every line, and brightness, and shadow fade away by degrees, as she came nearer and nearer to the Sun, until at last she sat completely lost in his dazzling rays! But--by the way--Barbican, are there any eclipses in the Moon?"

"O yes; solar eclipses" replied Barbican, "must always occur whenever the centres of the three heavenly bodies are in the same line, the Earth occupying the middle place. However, such eclipses must always be annular, as the Earth, projected like a screen on the solar disc, allows more than half of the Sun to be still visible."

"How is that?" asked M'Nicholl, "no total eclipses in the Moon? Surely the cone of the Earth's shadow must extend far enough to envelop her surface?"

"It does reach her, in one sense," replied Barbican, "but it does not in another. Remember the great refraction of the solar rays that must be produced by the Earth's atmosphere. It is easy to show that this refraction prevents the Sun from ever being totally invisible. See here!" he continued, pulling out his tablets, "Let _a_ represent the horizontal parallax, and _b_ the half of the Sun's apparent diameter--"

"Ouch!" cried the Frenchman, making a wry face, "here comes Mr. _x_ square riding to the mischief on a pair of double zeros again! Talk English, or Yankee, or Dutch, or Greek, and I'm your man! Even a little Arabic I can digest! But hang me, if I can endure your Algebra!"

"Well then, talking Yankee," replied Barbican with a smile, "the mean distance of the Moon from the Earth being sixty terrestrial radii, the length of the conic shadow, in consequence of atmospheric refraction, is reduced to less than forty-two radii. Consequently, at the moment of an eclipse, the Moon is far beyond the reach of the real shadow, so that she can see not only the border rays of the Sun, but even those proceeding from his very centre."

"Oh then," cried Ardan with a loud laugh, "we have an eclipse of the Sun at the moment when the Sun is quite visible! Isn't that very like a bull, Mr. Philosopher Barbican?"

"Yet it is perfectly true notwithstanding," answered Barbican. "At such a moment the Sun is not eclipsed, because we can see him: and then again he is eclipsed because we see him only by means of a few of his rays, and even these have lost nearly all their brightness in their pa.s.sage through the terrestrial atmosphere!"

"Barbican is right, friend Michael," observed the Captain slowly: "the same phenomenon occurs on earth every morning at sunrise, when refraction shows us

'_the Sun new ris'n Looking through the horizontal misty air, Shorn of his beams._'"

"He must be right," said Ardan, who, to do him justice, though quick at seeing a reason, was quicker to acknowledge its justice: "yes, he must be right, because I begin to understand at last very clearly what he really meant. However, we can judge for ourselves when we get there.--But, apropos of nothing, tell me, Barbican, what do you think of the Moon being an ancient comet, which had come so far within the sphere of the Earth's attraction as to be kept there and turned into a satellite?"

"Well, that _is_ an original idea!" said Barbican with a smile.

"My ideas generally are of that category," observed Ardan with an affectation of dry pomposity.

"Not this time, however, friend Michael," observed M'Nicholl.

"Oh! I'm a plagiarist, am I?" asked the Frenchman, pretending to be irritated.

"Well, something very like it," observed M'Nicholl quietly. "Apollonius Rhodius, as I read one evening in the Philadelphia Library, speaks of the Arcadians of Greece having a tradition that their ancestors were so ancient that they inhabited the Earth long before the Moon had ever become our satellite. They therefore called them [Greek: _Proselenoi_]

or _Ante-lunarians_. Now starting with some such wild notion as this, certain scientists have looked on the Moon as an ancient comet brought close enough to the Earth to be retained in its...o...b..t by terrestrial attraction."

"Why may not there be something plausible in such a hypothesis?" asked Ardan with some curiosity.

"There is nothing whatever in it," replied Barbican decidedly: "a simple proof is the fact that the Moon does not retain the slightest trace of the vaporous envelope by which comets are always surrounded."

"Lost her tail you mean," said Ardan. "Pooh! Easy to account for that!

It might have got cut off by coming too close to the Sun!"

"It might, friend Michael, but an amputation by such means is not very likely."

"No? Why not?"

"Because--because--By Jove, I can't say, because I don't know," cried Barbican with a quiet smile on his countenance.

"Oh what a lot of volumes," cried Ardan, "could be made out of what we don't know!"

"At present, for instance," observed M'Nicholl, "I don't know what o'clock it is."

"Three o'clock!" said Barbican, glancing at his chronometer.

"No!" cried Ardan in surprise. "Bless us! How rapidly the time pa.s.ses when we are engaged in scientific conversation! Ouf! I'm getting decidedly too learned! I feel as if I had swallowed a library!"

"I feel," observed M'Nicholl, "as if I had been listening to a lecture on Astronomy in the _Star_ course."

"Better stir around a little more," said the Frenchman; "fatigue of body is the best antidote to such severe mental labor as ours. I'll run up the ladder a bit." So saying, he paid another visit to the upper portion of the Projectile and remained there awhile whistling _Malbrouk_, whilst his companions amused themselves in looking through the floor window.

Ardan was coming down the ladder, when his whistling was cut short by a sudden exclamation of surprise.

"What's the matter?" asked Barbican quickly, as he looked up and saw the Frenchman pointing to something outside the Projectile.

Approaching the window, Barbican saw with much surprise a sort of flattened bag floating in s.p.a.ce and only a few yards off. It seemed perfectly motionless, and, consequently, the travellers knew that it must be animated by the same ascensional movement as themselves.

"What on earth can such a consarn be, Barbican?" asked Ardan, who every now and then liked to ventilate his stock of American slang. "Is it one of those particles of meteoric matter you were speaking of just now, caught within the sphere of our Projectile's attraction and accompanying us to the Moon?"

"What I am surprised at," observed the Captain, "is that though the specific gravity of that body is far inferior to that of our Projectile, it moves with exactly the same velocity."

"Captain," said Barbican, after a moment's reflection, "I know no more what that object is than you do, but I can understand very well why it keeps abreast with the Projectile."

"Very well then, why?"

"Because, my dear Captain, we are moving through a vacuum, and because all bodies fall or move--the same thing--with equal velocity through a vacuum, no matter what may be their shape or their specific gravity. It is the air alone that makes a difference of weight. Produce an artificial vacuum in a gla.s.s tube and you will see that all objects whatever falling through, whether bits of feather or grains of shot, move with precisely the same rapidity. Up here, in s.p.a.ce, like cause and like effect."

"Correct," a.s.sented M'Nicholl. "Everything therefore that we shall throw out of the Projectile is bound to accompany us to the Moon."

"Well, we _were_ smart!" cried Ardan suddenly.

"How so, friend Michael?" asked Barbican.

"Why not have packed the Projectile with ever so many useful objects, books, instruments, tools, et cetera, and fling them out into s.p.a.ce once we were fairly started! They would have all followed us safely! Nothing would have been lost! And--now I think on it--why not fling ourselves out through the window? Shouldn't we be as safe out there as that bolide? What fun it would be to feel ourselves sustained and upborne in the ether, more highly favored even than the birds, who must keep on flapping their wings continually to prevent themselves from falling!"