o make a direct measurement of it, have yielded discordant
results. At one time, for instance, Lord Rosse believed he had
demonstrated that at lunar noon the temperature of the rocks rose above
the boiling-point of water. But afterward he changed his mind and
favored the theory of a low temperature.

In this and in other respects much remains to be discovered concerning
our interesting satellite, and there is plenty of room, and an abundance
of original occupation, for new observers of the lunar world.

CHAPTER IX

HOW TO FIND THE PLANETS

There is no reason why everybody should not know the principal planets
at sight nearly as well as everybody knows the moon. It only requires a
little intelligent application to become acquainted with the other
worlds that have been discussed in the foregoing chapters, and to be
able to follow their courses through the sky and recognize them wherever
they appear. No telescope, or any other instrument whatever, is required
for the purpose. There is but one preliminary requirement, just as every
branch of human knowledge presupposes its A B C. This is an acquaintance
with the constellations and the principal stars--not a difficult thing
to obtain.

Almost everybody knows the "Great Dipper" from childhood's days,
except, perhaps, those who have had the misfortune to spend their youth
under the glare of city lights. Some know Orion when he shines
gloriously in the winter heavens. Many are able to point out the north
star, or pole star, as everybody should be able to do. All this forms a
good beginning, and may serve as the basis for the rapid acquirement of
a general knowledge of the geography of the heavens.

If you are fortunate enough to number an astronomer among your
acquaintance--an amateur will do as well as a professor--you may, with
his aid, make a short cut to a knowledge of the stars. Otherwise you
must depend upon books and charts. My Astronomy with an Opera-Glass was
prepared for this very purpose. For simply learning the constellations
and the chief stars you need no opera-glass or other instrument. With
the aid of the charts, familiarize yourself with the appearance of the
constellations by noticing the characteristic arrangements of their
chief stars. You need pay no attention to any except the bright stars,
and those that are conspicuous enough to thrust themselves upon your
attention.

Learn by observation at what seasons particular constellations are on,