pest of the visible craters on the Moon. It has
a diameter of 64 miles, and the inner edge of the ring rises from the
level floor to a height ranging from 14,000 to 18,000 feet. A group of
mountains occupies the centre of the area, the highest peak of which
reaches an elevation of 5,200 feet. Cyrillus and Catharina, two adjacent
craters, are each about 16,000 feet deep and connected by a wide valley.

(6) Aristarchus is the brightest spot on the Moon, and appears almost
dazzling in the telescope. The crater has a diameter of 42 miles, the
centre of which is occupied by a steep mountain. The rampart on the
western side rises to a height of 7,500 feet, on the east it becomes a
plateau which connects it with a smaller crater called Herodotus. Bright
streaks radiate from Aristarchus when there is full moon, and extend for
a considerable distance over the surface of the orb.

Though the face of the Moon has been carefully scanned for two centuries
and a half, and selenographers have mapped and delineated her features
with the utmost accuracy and precision, yet no perceptible change of a
reliable character has been perceived to occur on any part of the orb.
The surface of the hemisphere directed towards the Earth appears to be
an alternation of desert plains, craggy wildernesses, and extinct
volcanoes--a region of desolation unoccupied by any living thing, and
'upon which the light of life has never dawned.' Owing to the absence of
an atmosphere, there is neither diffuse daylight nor twilight on the
Moon. Every portion of the lunar surface not exposed to the Sun's rays
is shrouded in darkness, and black shadows can be observed fringing
prominences of silvery whiteness. If the Moon were enveloped in an
atmosphere similar to that which surrounds the Earth, the reflection and
diffusion of light among the minute particles of watery vapour which
permeate it would give rise to a gradual transition from light to
darkness; the lunar surface would be visible when not illumined by the
direct rays of the Sun, and before sunrise and after sunset, dawn and
twilight would occur as upon the Earth. But upon the Moon there is no
dawn, and the darkness of night envelops the orb until the appearance of
the edge of the Sun's disc above the horizon, then his dazzling rays
illumine the summits and loftiest peaks of the lunar mountains whilst
yet their sides and bases are wrapped in deep gloom. Since the pace of
the Sun across the lunar heavens is