| 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 that of the Apennines, about 450 miles long, a length, however, far inferior to that of many of the great mountain ranges of our globe. They skirt the western shores of the Mare Imbrium, over which they rise in immense cliffs, 18 or 20 thousand feet in height, steep as a wall and casting over the plain intensely black shadows at least 90 miles long. Of Mt. Huyghens, the highest in the group, the travellers were just barely able to distinguish the sharp angular summit in the far west. To the east, however, the Carpathians, extending from the 18th to 30th degrees of east longitude, lay directly under their eyes and could be examined in all the peculiarities of their distribution.
Barbican proposed a hypothesis regarding the formation of those mountains, which his companions thought at least as good as any other. Looking carefully over the Carpathians and catching occasional glimpses of semi-circular formations and half domes, he concluded that the chain must have formerly been a succession of vast craters. Then had come some mighty internal discharge, or rather the subsidence to which Mare Imbrium is due, for it immediately broke off or swallowed up one half of those mountains, leaving the other half steep as a wall on one side and sloping gently on the other to the level of the surrounding plains. The Carpathians were therefore pretty nearly in the same condition as the crater mountains Ptolemy, Alpetragius and Arzachel would find themselves in, if some terrible cataclysm, by tearing away their eastern ramparts, had turned them into a chain of mountains whose towering cliffs would nod threateningly over the western shores of Mare Nubium. The mean height of the Carpathians is about 6,000 feet, the altitude of certain points in the Pyrenees such as the Port of Pineda, or Roland's Breach, in the shadow of Mont Perdu. The northern slopes of the Carpathians sink rapidly towards the shores of the vast Mare Imbrium.
Towards two o'clock in the morning, Barbican calculated the Projectile to be on the 20th northern parallel, and therefore almost immediately over the little ring mountain called Pytheas, about 4600 feet in height. The distance of the travellers from the Moon at this point could not be more than about 750 miles, reduced to about 7 by means of their excellent telescopes.
Mare Imbrium, the Sea of Rains here revealed itself in all its vastness to the eyes of the travellers, though it must be acknowledged that the immense depression so called, did not afford them a very clear idea regarding its exact boundaries. Right ahead of them rose Lambert about a mile in height; and further on, more to the left, in the direction of Oceanus Procellarum, Euler revealed itself by its glittering radiations. This mountain, of about the same height as Lambert, had been the object of very interesting calculations on the part of Schroeter of Erfurt. This keen observer, desirous of inquiring into the probable origin of the lunar mountains, had proposed to himself the following question: Does the volume of the crater appear to be equal to that of the surrounding ramparts? His calculations showing him that this was generally the case, he naturally concluded that these ramparts must therefore have been the product of a single eruption, for successive eruptions of volcanic matter would have disturbed this correlation. Euler alone, he found, to be an exception to this general law, as the volume of its crater appeared to be twice as great as that of the mass surrounding it. It must therefore have been formed by several eruptions in succession, but in that case what had become of the ejected matter?
Theories of this nature and all manner of scientific questions were, of course, perfectly permissible to terrestrial astronomers laboring under the disadvantage of imperfect instruments. But Barbican could not think of wasting his time in any speculation of the kind, and now, seeing that his Projectile perceptibly approached the lunar disc, though he despaired of ever reaching it, he was more sanguine than ever of being soon able to discover positively and unquestionably some of the secrets of its formation.
CHAPTER XIII.
LUNAR LANDSCAPES
At half past two in the morning of December 6th, the travellers crossed the 30th northern parallel, at a distance from the lunar surface of 625 miles, reduced to about 6 by their spy-glasses. Barbican could not yet see the least probability of their landing at any point of the disc. The velocity of the Projectile was decidedly slow, but for that reason extremely puzzling. Barbican could not account for it. At such a proximity to the Moon, the velocity, one would think, should be very great indeed to be able to counteract the lunar attraction. Why did it not fall? Barbican could not tell; his companions were equally in the dark. Ardan said he gave it up. Besides they had no time to spend in investigating it. The lunar panorama was unrolling all its splendors beneath them, and they could not bear to lose one of its slightest details.