white rays are well seen only in full light of the sun at full moon,
just as the white snow in the crevasses of a glacier is seen bright
from a distance only when the sun is high, and disappears at
sunset. Then there are deep, narrow, crooked "rills" which may have
been water-courses; also "clefts" about half a mile wide, and often
hundreds of miles long, like deep cracks in the surface going straight
through mountain and valley.

The moon shares with the sun the advantage of being a good subject for
photography, though the planets are not. This is owing to her larger
apparent size, and the abundance of illumination. The consequence is
that the finest details of the moon, as seen in the largest telescope
in the world, may be reproduced at a cost within the reach of all.

No certain changes have ever been observed; but several suspicions
have been expressed, especially as to the small crater _Linne_, in the
_Mare Serenitatis_. It is now generally agreed that no certainty can
be expected from drawings, and that for real evidence we must await
the verdict of photography.

No trace of water or of an atmosphere has been found on the moon. It
is possible that the temperature is too low. In any case, no
displacement of a star by atmospheric refraction at occultation has
been surely recorded. The moon seems to be dead.

The distance of the moon from the earth is just now the subject of
re-measurement. The base line is from Greenwich to Cape of Good Hope,
and the new feature introduced is the selection of a definite point on
a crater (Mosting A), instead of the moon's edge, as the point whose
distance is to be measured.