CHAP. IV. _The Phenomena of the Heavens as seen from different parts of the Earth._ [Sidenote: We are kept to the Earth by gravity. PLATE II. Fig. I. Antipodes. Axis of the World. It’s Poles. Fig. II.] 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.]