A bare view of the Figure is enough to shew, that as the Earth advances
from Capricorn toward Aries, and the Sun appears to move from Cancer
toward Libra, the north Pole recedes toward the dark, which causes the
days to decrease, and the nights to increase in length, till the Earth
comes to Aries, and then they are equal as before; for the boundary of
light and darkness cut the Equator and all it’s parallels equally, or in
halves. The north pole then goes into the dark, and continues therein
until the Earth goes half way round it’s Orbit; or, from the 23d of
_September_ till the 20th of _March_. In the middle between these times,
_viz._ on the 22d of _December_, the north Pole is as far as it can be
in the dark, which is 23-1/2 degrees, equal to the inclination of the
Earth’s Axis from a perpendicular to it’s Orbit: and then, the northern
parallels are as much in the dark as they were in the light on the 21 of
_June_; the winter nights being as long as the summer days, and the
winter days as short as the summer nights. It is needless to multiply
words on this subject, as we shall have occasion to mention the seasons
again in describing the _Orrery_, § 439. Only this must be noted, that
all that has been said of the northern Hemisphere, the contrary must be
understood of the southern; for on different sides of the Equator the
seasons are contrary, because, when the northern Hemisphere inclines
toward the Sun the southern declines from him.
[Sidenote: The Phenomena of Saturn’s Ring.