122. We are kept to the Earth’s surface on all sides by the power of
it’s central attraction; which, laying hold of all bodies according to
their densities or quantities of matter without regard to their bulks,
constitutes what we call their _weight_. And having the sky over our
heads, go where we will, and our feet towards the centre of the Earth,
we call it _up_ over our heads, and _down_ under our feet: although the
same right line which is _down_ to us, if continued through and beyond
the opposite side of the Earth, would be _up_ to the inhabitants on the
opposite side. For, the inhabitants _n_, _i_, _e_, _m_, _s_, _o_, _q_,
_l_ stand with their feet toward the Earth’s centre _C_; and have the
same figure of sky _N_, _l_, _E_, _M_, _S_, _O_, _Q_, _L_ over their
heads. Therefore, the point _S_ is as directly upward to the inhabitant
_s_ on the south Pole as _N_ is to the inhabitant _n_ on the North Pole:
so is _E_ to the inhabitant _e_, supposed to be on the north end of
_Peru_; and _Q_ to the opposite inhabitant _q_ on the middle of the
island _Sumatra_. Each of these observers is surprised that his opposite
or _Antipode_ can stand with his head hanging downwards. But let either
go to the other, and he will tell him that he stood as upright and firm
on the place where he was as he now stands where he is. To all these
observers the Sun, Moon, and Stars seem to turn round the points _N_ and
_S_ as the Poles of the fixed Axis _NCS_; because the Earth does really
turn round the mathematical line _nCs_ as round an Axis of which _n_ is
the North Pole and _s_ the South Pole. The Inhabitant _U_ (Fig. II.)
affirms that he is on the uppermost side of the Earth, and wonders how
another at _L_ can stand on the undermost side with his head hanging
downwards. But _U_ in the mean time forgets that in twelve hours time he
will be carried half round with the Earth; and then be in the very
situation that _L_ now is, although as far from him as before. And yet,
when _U_ comes there, he will find no difference as to his manner of
standing; only he will see the opposite half of the Heavens, and imagine
the Heavens to have gone half round him.
[Sidenote: How our Earth might have an upper and an under side.]
123. When we see a globe hung up in a room we cannot help imagining it
to have an upper and an under side, and immediately form a like idea of
the Earth; from whence we conclude, that it is as impossible for persons
to stand on the under side of the Earth as for pebbles to lie on the
under side of a common Globe, which instantly fall down from it to the
ground; and well they may, because the attraction of the Earth, being
too strong for the attraction of the Globe, pulls them away. Just so
would be the case with our Earth, if it were placed near a Globe much
bigger than itself, such as Jupiter: for then it would really have an
upper and an under side with respect to that large Globe; which, by it’s
Attraction, would pull away every thing from the side of the Earth next
to it; and only those on the top of the opposite or upper side could
keep upon it. But there is no larger Globe near enough our Earth to
overcome it’s central attraction; and therefore it has no such thing as
an upper and an under side: for all bodies on or near it’s surface, even
to the Moon, gravitate towards it’s center.
[Sidenote: PLATE II.]
124. Let any man imagine that the Earth and every thing but himself is
taken away, and he left alone in the midst of indefinite Space; he could
then have no idea of _up_ or _down_; and were his pockets full of gold,
he might take the pieces one by one, and throw them away on all sides of
him, without any danger of losing them; for the attraction of his body
would bring them all back by the ways they went, and _he_ would be
_down_ to every one of them. But then, if a Sun or any other large body
were created, and placed in any part of Space several millions of miles
from him, he would be attracted towards it, and could not save himself
from falling _down_ to it.
[Sidenote: Fig. I.
One half of the Heavens visible to an inhabitant on any part
of the Earth.
Phenomena at the Poles.