338. As seen from the Sun or Moon, the Earth’s Axis appears differently inclined every day of the year, on account of keeping its parallelism throughout its annual course. Let _E_, _D_, _O_, _N_, be the Earth at the two Equinoxes and the two Solstices; _N S_ its Axis, _N_ the North Pole, _S_ the South Pole, _Æ Q_ the Equator, _T_ the Tropic of Cancer, _t_ the Tropick of Capricorn, and _ABC_ the Circumference of the Earth’s enlightened Disc as seen from the Sun or New Moon at these times. The Earth’s Axis has the position _NES_ at the vernal Equinox, lying towards the right hand, as seen from the Sun or New Moon; its Poles _N_ and _S_ being then in the Circumference of the Disc; and the Equator and all its parallels seem to be straight lines, because their planes pass through the observer’s eye looking down upon the Earth from the Sun or Moon directly over _E_, where the Ecliptic _FG_ intersects the Equator _Æ_. At the Summer Solstice, the Earth’s Axis has the position _NDS_; and that part of the Ecliptic _FG_ in which the Moon is then New, touches the Tropic of Cancer _T_ at _D_. The North Pole _N_ at that time inclining 23-1/2 degrees towards the Sun, falls so many degrees within the Earth’s enlightened Disc, because the Sun is then vertical to _D_, 23-1/2 degrees north of the Equator _ÆQ_; and the Equator with all its parallels seem elliptic curves bending downward, or towards the South Pole as seen from the Sun: which Pole, together with 23-1/2 degrees all round it, is hid behind the Disc in the dark Hemisphere of the Earth. At the autumnal Equinox the Earth’s Axis has the position _NOS_, lying to the left hand as seen from the Sun or New Moon, which are then vertical to _O_, where the Ecliptic cuts the Equator _ÆQ_. Both Poles now lie in the circumference of the Disc, the North Pole just going to disappear behind it, and the South Pole just entering into it; and the Equator with all its parallels seem to be straight lines, because their planes pass through the observer’s eye, as seen from the Sun, and very nearly so as seen from the Moon. At the Winter Solstice the Earth’s Axis has the position _NNS_; when its South Pole _S_ inclining 23-1/2 degrees toward the Sun falls 23-1/2 degrees within the enlightened Disc, as seen from the Sun or New Moon which are then vertical to the Tropic of Capricorn _t_, 23-1/2 degrees south of the Equator _ÆQ_; and the Equator with all its parallels seem elliptic curves bending upward; the North Pole being as far hid behind the Disc in the dark Hemisphere, as the South Pole is come into the light. The nearer that any time of the year is to the Equinoxes or Solstices, the more it partakes of the Phenomena relating to them. [Sidenote: PLATE XI. Various positions of the Earth’s Axis, as seen from the Sun at different times of the year.]