47. The EARTH is the next Planet above Venus in the System. It is 81
millions of miles from the Sun, and goes round him (as in the circle ⊕)
in 365 days 5 hours 49 minutes, from any Equinox or Solstice to the same
again: but from any fixed Star to the same again, as seen from the Sun,
in 365 days 6 hours and 9 minutes; the former being the length of the
Tropical year, and the latter the length of the Sidereal. It travels at
the rate of 58 thousand miles every hour, which motion, though 120 times
swifter than that of a cannon ball, is little more than half as swift as
Mercury’s motion in his Orbit. The Earth’s diameter is 7970 miles; and
by turning round it’s Axis every 24 hours from West to East, it causes
an apparent diurnal motion of all the heavenly Bodies from East to West.
By this rapid motion of the Earth on it’s Axis, the inhabitants about
the Equator are carried 1042 miles every hour, whilst those on the
parallel of _London_ are carried only about 580, besides the 58 thousand
miles by the annual motion above-mentioned, which is common to all
places whatever.
[Sidenote: Inclination of it’s Axis.]
48. The Earth’s Axis makes an angle of 23-1/2 degrees with the Axis of
it’s Orbit; and keeps always the same oblique direction; inclining
towards the same fixed Stars[12] throughout it’s annual course; which
causes the returns of spring, summer, autumn, and winter; as will be
explained at large in the tenth Chapter.
[Sidenote: A proof of it’s being round.]
49. The Earth is round like a globe; as appears, 1. from it’s shadow in
Eclipses of the Moon; which shadow is always bounded by a circular line
§ 314. 2. From our seeing the masts of a ship whilst the hull is hid by
the convexity of the water. 3. From it’s having been sailed round by
many navigators. The hills take off no more from the roundness of the
Earth in comparison, than grains of dust do from the roundness of a
common Globe.
[Sidenote: It’s number of square miles.]
50. The seas and unknown parts of the Earth (by a measurement of the
best Maps) contain 160 million 522 thousand and 26 square miles; the
inhabited parts 38 million 990 thousand 569: _Europe_ 4 million 456
thousand and 65; _Asia_ 10 million 768 thousand 823; _Africa_ 9 million
654 thousand 807; _America_ 14 million 110 thousand 874. In all, 199
million 512 thousand 595; which is the number of square miles on the
whole surface of our Globe.
[Sidenote: The proportion of land and sea.