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Twins, Castor, and Pollux : S. 65° E. and 35° in height, is the bright star Regulus, or Cor Leonis : exactly in the east, and 22 high, is the star Deneb Alased in the Lion's tail: 30 from the east towards the north, Arcturus is about 3° above the horizon : directly over Arcturus, and 31° above the horizon, is Cor Caroli: in the north-east are the stars in the extremity of the Great Bear's tail; Aleath, the first star in the tail, and Dubhe, the northernmost Pointer in the same constellation: the altitude of the first of these is 30, that of the second 41°, and that of the third 56o.
Reckoning westward, we see the beautiful constellation Orion; the middle star of the three in his belt, is S. 20 W. its altitude 35°: nine degrees below the belt, and a little more to the west, is Rigel, the bright star in his heel : above his belt, in a straight line drawn from Rigel between the middle and most northward in his belt, and 9* above it, is the bright star in his shoulder : S. 49° W. and 45 above the horizon, is Aldebaran, the southern eye of the Bull: a little to the west of Aldebaran, are the Hyades : the same altitude, and about S. 70° W. are the Pleiades : in the W. by S. point is ! apella in Auriga, its altitude 73°: in the north-west, and about 42 high, is the constellation Cassiopeia : and almost in the north, near the horizon, is the constellation Cygnus."
* Bransby's Use of the Globes.
PROBLEM XVIII. To trace the circles of the sphere
in the starry firmament.
I shall solve this problem for the time of the autumnal equinox; because that intersection of the equator and ecliptic will be directly under the depressed part of the meridian about midnight; and then the opposite intersection will be elevated above the horizon; and also because our first meridian upon the terrestrial globe passing through London and the first point of Aries, when both globes are rectified to the latitude of London and to the sun's place, and the first point of Aries is brought under the graduated side of each of their meridians, we shall have the corresponding face of the heavens and the earth represented as they are with respect to each other at that time, and the principal circles of each sphere will correspond with each other.
The horizon is then distinguished, if we begin from the north and count westward, by the following constellations; the hounds and waist of Bootes, the northern crown, the head of Hercules, the shoulders of Serpentarius, and the Sobieski's shield; it
passes a little below the feet of Antinous, and through those of Capricorn, through the Sculptor's frame, Eridanus, the star Rigel in Orion's foot, the head of Monoceros, the Crab, the head of the Little Lion, and lower part of the Great Bear.
The meridian is then represented by the equinoc · tial colure, which passes through the star marked a
in the tail of the Little Bear, under the north pole, the pole star, one of the stars in the back of Cassiopeia's chair marked B, the head of Andromeda, the bright star in the wing of Pegasus marked y, and the extremity of the tail of the Whale.
That part of the equator which is then above the horizon, is distinguished on the western side by the northern part of Sobieski's shield, the shoulder of Antinous, the head and vessel of Aquarius, the belly of the western fish in Pisces; it passes through the head of the Whale, and a bright star marked s in the corner of his mouth, and thence through the star marked ; in the belt of Orion, at that time near the eastern side of the horizon.
That half of the ecliptic which is then above the horizon, if we begin from the western side, presents to our view Capricornus, Aquarius, Pisces, Aries, Taurus, Gemini, and a part of the constellation Cancer.
The solstitial colure, from the western side, passes through Cerberus and the hand of Hercules, thence by the western side of the constellation Lyra, and through the Dragon's head and body, through the pole point under the polar star, to the east of Auriga, through the star marked n in the foot of Castor, and through the hand and elbow of Orion.
The northern polar circle, from that part of the meridian under the elevated pole, advancing towards the west, passes through the shoulder of the Great Bear, thence a little to the north of the star marked a in the Dragon's tail, the great knot of the Dragon,
the middle of the body of Cepheus, the northern part of Cassiopeia, and base of her throne, through Camelopardalus, and the head of the Great Bear.
The tropic of Cancer, from the western edge of the horizon, passes under the arm of Hercules, under the Vulture, through the Goose and Fox, which is under the beak and wing of the Swan, under the star called Sheat, marked R, in Pegasus, under the head of Andromeda, and through the star marked 0, in the fish of the constellation Pisces, above the bright star in the head of the Ram, marked a, through the Pleiades, between the horns of the Bull, and through a group of stars at the foot of Castor, thence above a star marked a, between Castor and Pollux, and so through a part of the constellation Cancer, where it disappears by passing under the eastern part of the horizon.
The tropic of Capricorn, from the western side of the horizon, passes through the belly and under the tail of Capricorn, thence under Aquarius, through a star in Eridanus marked c, thence under the belly of the Whale, through the base of the Chemical Furnace, whence it goes under the Hare, at the feet of Orion, being there depressed under the horizon.
The southern polar circle is invisible to the inhabitants of London, by being under our horizon.
ARCTIC AND ANTARCTIC CIRCLES, OR CIRCLES OF
PERPETUAL APPARITION AND OCCULTATION.
The largest parallel of latitude on the terrestrial
globe, as well as the largest circle of declination on the celestial, that appears entire above the horizon of any place in north latitude, was called by the ancients the arctic circle, or circle of perpetual apparition.
Between the arctic circle and the north pole in the celestial sphere, are contained all those stars which never set at that place, and seem to us, by the rotative motion of the earth, to be perpetually carried round above our horizon in cireles parallel to the equator.
The largest parallel of latitude on the terrestrial, and the largest parallel of declination to the celestial globe, which is entirely hid below the horizon of any place, was by the ancients called the antarctic circle, or circle of perpetual occultation.
This circle includes all the stars which never rise in that place to an inhabitant of the northern hemisphere, but are perpetually below the horizon.
All arctic circles touch their horizons in the north point, and all antarctic circles touch their horizons in the south point; which point, in the terrestrial and celestial spheres, is the intersection of the meridian and horizon.
If the elevation of the pole be 45 degrees, the most elevated part either of the arctic or antarctic circle will be the zenith of the place.
If the pole's elevation be less than 45 degrees, the zenith point of those places will fall without its arctic or antarctic circle; if greater, it will fall within.