ie;
while at the north pole itself, the sun would always run round and round
the horizon. Similarly, the more south one went from the equator the
more northerly would the path of the sun lie, while at the south pole it
would be seen to skirt the horizon in the same manner as at the north
pole. The result of such an arrangement would be, that each place upon
the earth would always have one unvarying climate; in which case there
would not exist any of those beneficial changes of season to which we
owe so much.

The changes of season, which we fortunately experience, are due,
however, to the fact that the sun does not appear to move across the sky
each day at one unvarying altitude, but is continually altering the
position of its path; so that at one period of the year it passes across
the sky low down, and remains above the horizon for a short time only,
while at another it moves high up across the heavens, and is above the
horizon for a much longer time. Actually, the sun seems little by little
to creep up the sky during one half of the year, namely, from mid-winter
to mid-summer, and then, just as gradually, to slip down it again during
the other half, namely, from mid-summer to mid-winter. It will therefore
be clear that every region of the earth is much more thoroughly warmed
during one portion of the year than during another, _i.e._ when the
sun's path is high in the heavens than when it is low down.

Once more we find appearances exactly the contrary from the truth. The
earth is in this case the real cause of the deception, just as it was in
the other cases. The sun does not actually creep slowly up the sky, and
then slowly dip down it again, but, owing to the earth's axis being set
aslant, different regions of the earth's surface are presented to the
sun at different times. Thus, in one portion of its orbit, the northerly
regions of the earth are presented to the sun, and in the other portion
the southerly. It follows of course from this, that when it is summer in
the northern hemisphere it is winter in the southern, and _vice versa_
(see Fig. 13, p. 176).

[Illustration: FIG. 13.--Summer and Winter.]

The fact that, in consequence of this slant of the earth's axis, the sun
is for part of the year on the north side of the equator and part of the
year on the south side, leads to a very peculiar result. The path of the
moon around the earth is nearly on the same plane with the earth's path
around the sun. The moo