y 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 Projecti