square miles. South of _Oceanus Procellarum_ and separated
from _Mare Nubium_ by a goodly number of ring mountains, lies the little
basin of _Mare Humorum_, the Sea of Humors, containing only about 66
thousand square miles, its central point having a latitude of 25 deg. south
and a longitude of 40 deg. east.

On the shores of these great seas three "Gulfs" are easily found: _Sinus
Aestuum_, the Gulf of the Tides, northeast of the centre; _Sinus
Iridium_, the Gulf of the Rainbows, northeast of the _Mare Imbrium_; and
_Sinus Roris_, the Dewy Gulf, a little further northeast. All seem to be
small plains enclosed between chains of lofty mountains.

The western hemisphere, dedicated to the ladies, according to Ardan, and
therefore naturally more capricious, was remarkable for "seas" of
smaller dimensions, but much more numerous. These were principally:
_Mare Serenitatis_, the Sea of Serenity, 25 deg. north and 20 deg. west,
comprising a surface of about 130 thousand square miles; _Mare Crisium_,
the Sea of Crises, a round, well defined, dark depression towards the
northwestern edge, 17 deg. north 55 deg. west, embracing a surface of 60
thousand square miles, a regular Caspian Sea in fact, only that the
plateau in which it lies buried is surrounded by a girdle of much higher
mountains. Then towards the equator, with a latitude of 5 deg. north and a
longitude of 25 deg. west, appears _Mare Tranquillitatis_, the Sea of
Tranquillity, occupying about 180 thousand square miles. This
communicates on the south with _Mare Nectaris_, the Sea of Nectar,
embracing an extent of about 42 thousand square miles, with a mean
latitude of 15 deg. south and a longitude of 35 deg. west. Southwest from _Mare
Tranquillitatis_, lies _Mare Fecunditatis_, the Sea of Fertility, the
greatest in this hemisphere, as it occupies an extent of more than 300
thousand square miles, its latitude being 3 deg. south and its longitude 50 deg.
west. For away to the north, on the borders of the _Mare Frigoris_, or
Icy Sea, is seen the small _Mare Humboldtianum_, or Humboldt Sea, with a
surface of about 10 thousand square miles. Corresponding to this in the
southern hemisphere lies the _Mare Australe_, or South Sea, whose
surface, as it extends along the western rim, is rather difficult to
calculate. Finally, right in the centre of the lunar disc, where the
equator intersects the first meridian, can be seen _Sinus Medii_, the
Central Gulf, the common property theref