enitatis (Sea of Serenity), has
appeared to undergo slight changes, and is even said to have been
invisible for a while (see Plate X., p. 200). It is, however, believed
that the changes in question may be due to the varying angles at which
the sunlight falls upon the crater; for it is an understood fact that
the irregularities of the moon's motion give us views of her surface
which always differ slightly.

The suggestion has more than once been put forward that the surface of
the moon is covered with a thick layer of ice. This is generally
considered improbable, and consequently the idea has received very
little support. It first originated with the late Mr. S.E. Peal, an
English observer of the moon, and has recently been resuscitated by the
German observer, Herr Fauth.

The most unfavourable time for telescopic study of the moon is when she
is full. The sunlight is then falling directly upon her visible
hemisphere, and so the mountains cast no shadows. We thus do not get
that impression of hill and hollow which is so very noticeable in the
other phases.

The first map of the moon was constructed by Galileo. Tobias Mayer
published another in 1775; while during the nineteenth century greatly
improved ones were made by Beer and Maedler, Schmidt, Neison and others.
In 1903, Professor W.H. Pickering brought out a complete photographic
lunar atlas; and a similar publication has recently appeared, the work
of MM. Loewy and Puiseux of the Observatory of Paris.

The so-called "seas" of the moon are, as we have seen, merely dark
areas, and there appears to be no proof that they were ever occupied by
any liquid. They are for the most part found in the _northern_ portion
of the moon; a striking contrast to our seas and oceans, which take up
so much of the _southern_ hemisphere of the earth.

There are many erroneous ideas popularly held with regard to certain
influences which the moon is supposed to exercise upon the earth. For
instance, a change in the weather is widely believed to depend upon a
change in the moon. But the word "change" as here used is meaningless,
for the moon is continually changing her phase during the whole of her
monthly round. Besides, the moon is visible over a great portion of the
earth _at the same moment_, and certainly all the places from which it
can then be seen do not get the same weather! Further, careful
observations, and records extending over the past one hundred years and
more, fail to s