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.