theory of yours holds no more water than mine, Ardan," observed M'Nicholl.
"Correct, Captain," replied the Frenchman; "Barbican has a trick of knocking the bottom out of every weaker vessel. But let us hear what he has to say on the subject himself. What is your theory. Barbican?"
"My theory," said Barbican, "is pretty much the same as that lately presented by an English astronomer, Nasmyth, who has devoted much study and reflection to lunar matters. Of course, I only formulate my theory, I don't affirm it. These streaks are cracks, made in the Moon's surface by cooling or by shrinkage, through which volcanic matter has been forced up by internal pressure. The sinking ice of a frozen lake, when meeting with some sharp pointed rock, cracks in a radiating manner: every one of its fissures then admits the water, which immediately spreads laterally over the ice pretty much as the lava spreads itself over the lunar surface. This theory accounts for the radiating nature of the streaks, their great and nearly equal thickness, their immense length, their inability to cast a shadow, and their invisibility at any time except at or near the Full Moon. Still it is nothing but a theory, and I don't deny that serious objections may be brought against it."
"Do you know, dear boys," cried Ardan, led off as usual by the slightest fancy, "do you know what I am thinking of when I look down on the great rugged plains spread out beneath us?"
"I can't say, I'm sure," replied Barbican, somewhat piqued at the little attention he had secured for his theory.
"Well, what are you thinking of?" asked M'Nicholl.
"Spillikins!" answered Ardan triumphantly.
"Spillikins?" cried his companions, somewhat surprised.
"Yes, Spillikins! These rocks, these blocks, these peaks, these streaks, these cones, these cracks, these ramparts, these escarpments,—what are they but a set of spillikins, though I acknowledge on a grand scale? I wish I had a little hook to pull them one by one!"
"Oh, do be serious, Ardan!" cried Barbican, a little impatiently.
"Certainly," replied Ardan. "Let us be serious, Captain, since seriousness best befits the subject in hand. What do you think of another comparison? Does not this plain look like an immense battle field piled with the bleaching bones of myriads who had slaughtered each other to a man at the bidding of some mighty Caesar? What do you think of that lofty comparison, hey?"
"It is quite on a par with the other," muttered Barbican.
"He's hard to please, Captain," continued Ardan, "but let us try him again! Does not this plain look like—?"
"My worthy friend," interrupted Barbican, quietly, but in a tone to discourage further discussion, "what you think the plain looks like is of very slight import, as long as you know no more than a child what it really is!"
"Bravo, Barbican! well put!" cried the irrepressible Frenchman. "Shall I ever realize the absurdity of my entering into an argument with a scientist!"
But this time the Projectile, though advancing northward with a pretty uniform velocity, had neither gained nor lost in its nearness to the lunar disc. Each moment altering the character of the fleeting landscape beneath them, the travellers, as may well be imagined, never thought of taking an instant's repose. At about half past one, looking to their right on the west, they saw the summits of another mountain; Barbican, consulting his map, recognized Eratosthenes.
This was a ring mountain, about 33 miles in diameter, having, like Copernicus, a crater of immense profundity containing central cones. Whilst they were directing their glasses towards its gloomy depths, Barbican mentioned to his friends Kepler's strange idea regarding the formation of these ring mountains. "They must have been constructed," he said, "by mortal hands."
"With what object?" asked the Captain.
"A very natural one," answered Barbican. "The Selenites must have undertaken the immense labor of digging these enormous pits at places of refuge in which they could protect themselves against the fierce solar rays that beat against them for 15 days in succession!"
"Not a bad idea, that of the Selenites!" exclaimed Ardan.
"An absurd idea!" cried M'Nicholl. "But probably Kepler never knew the real dimensions of these craters. Barbican knows the trouble and time required to dig a well in Stony Hill only nine hundred feet deep. To dig out a single lunar crater would take hundreds and hundreds of years, and even then they should be giants who would attempt it!"
"Why so?" asked Ardan. "In the Moon, where gravity is six times less than on the Earth, the labor of the Selenites can't be compared with that of men like us."
"But suppose a Selenite to be six times smaller than a man like us!" urged M'Nicholl.
"And suppose a Selenite never had an existence at all!" interposed Barbican with his usual success in putting an end to the argument. "But never mind the Selenites now. Observe Eratosthenes as long as you have the opportunity."
"Which will not be very long," said M'Nicholl. "He is already sinking out of view too far to the right to be carefully observed."
"What are those peaks beyond him?" asked Ardan.
"The Apennines," answered Barbican; "and those on the left are the Carpathians."
"I have seen very few mountain chains or ranges in the Moon," remarked Ardan, after some minutes' observation.
"Mountains chains are not numerous in the Moon," replied Barbican, "and in that respect her oreographic system presents a decided contrast with that of the Earth. With us the ranges are many, the craters few; in the Moon the ranges are few and the craters innumerable."
Barbican might have spoken of another curious feature regarding the mountain ranges: namely, that they are chiefly confined to the northern hemisphere, where the craters are fewest and the "seas" the most extensive.
For the benefit of those interested, and to be done at once with this part of the subject, we give in the following little table a list of the chief lunar mountain chains, with their latitude, and respective heights in English feet.
| Name | Degrees of Latitude | Height | ||
| Southern Hemishpere. |
 |
Altai Mountains Cordilleras Pyrenees Riphean | 17° to 28 10 to 20 8 to 18 5 to 10 | 13,000ft. 12,000 12,000 2,600 |
| Northern Hemishpere. |
 |
Haemus Carpathian Apennines Taurus Hercynian Caucasus Alps | 10 to 20 15 to 19 14 to 27 25 to 34 17 to 29 33 to 40 42 to 30 | 6,300 6,000 18,000 8,500 3,400 17,000 10,000 |
Of these different chains, the most important is
