Galilei, Galileo, The systems of the world, 1661

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1deſcribed within the ſame, and neerer to the pole A, ſhall wholly
be included in the illuminated part; as on the contrary, the
poſite ones towards the Pole B, contained within the
lel L M, ſhall remain in the dark.
Moreover, the arch A I
ing equal to the arch F D, and the arch A F, common to them
both, the two arches I K F and A F D ſhall be equal, and each
a quadrant or 90 degrees.
And becauſe the whole arch I F M
is a ſemicircle, the arch F M ſhall be a quadrant, and equal to
the other F K I; and therefore the Sun O ſhall be in this ſtate
of the Earth vertical to one that ſtands in the point F.
But by
the revolution diurnal about the ſtanding Axis A B, all the points
of the parallel E F paſſe by the ſame point F: and therefore in
that ſame day the Sun, at noon, ſhall be vertical to all the
bitants of the Parallel E F, and will ſeem to them to deſcribe in its
apparent motion the circle which we call the Tropick of Cancer.
But to the inhabitants of all the Parallels that are above the
rallel E F, towards the North pole A, the Sun declineth from
their Vertex or Zenith towards the South; and on the contrary,
to all the inhabitants of the Parallels that are beneath E F,
wards the Equinoctial C D, and the South Pole B, the Meridian
Sun is elevated beyond their Vertex towards the North Pole A.
Next, it is viſible that of all the Parallels, only the greateſt C D
is cut in equal parts by the Terminator of the light I M.
But
the reſt, that are beneath and above the ſaid grand circle, are all
interſected in parts unequal: and of the ſuperiour ones, the
midiurnal arches, namely thoſe of the part of the Terreſtrial
face, illuſtrated by the Sun, are bigger than the ſeminocturnal
ones that remain in the dark: and the contrary befalls in the
remainder, that are under the great one C D, towards the pole B,
of which the ſemidiurnal arches are leſſer than the ſeminocturnal,
It is likewiſe apparently manifeſt, that the differences of the ſaid
arches go augmenting, according as the Parallels are neerer to
the Poles, till ſuch time as the parallel I K comes to be wholly in
the part illuminated, and the inhabitants thereof have a day of
twenty four hours long, without any night; and on the contrary,
the Parallel L M, remaining all in obſcurity, hath a night of
twenty four hours, without any day.
Come we next to the
third Figure of the Earth, placed with its centre in the point
Cancer, where the Sun ſeemeth to be in the firſt point of
pricorn.
We have already ſeen very manifeſtly, that by reaſon
the Axis A B doth not change inclination, but continueth
lel to it ſelf, the aſpect and ſituation of the Earth is the ſame to
an hair with that in the firſt Figure; ſave onely that that
ſphere which in the firſt was illuminated by the Sun, in this
maineth obtenebrated, and that cometh to be luminous, which in

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