The Sphere of the World with Commentaries

toward the north is called septentrional, or boreal, or arctic. And those six signs which are from the beginning of Aries to the end of Virgo are called septentrional signs. The other part of the zodiac which declines from the equinoctial toward the south is called meridional, or austral, or antarctic. And the six signs which are from the beginning of Libra to the end of Pisces are called meridional or austral. However, when it is said that the sun is in Aries or in another sign, it must be known that this preposition "in" is taken as "under," according to how we now understand "sign." But in another signification, a sign is called a quadrilateral pyramid, the base of which is that surface that we call a sign, while its vertex is at the center of the earth. And speaking properly according to this, we can say that the planets are in the signs.

In a third way, "sign" is spoken of so that it is understood as six circles passing over the poles of the zodiac and through the beginnings of the 12 signs. Those six circles divide the entire surface of the sphere into 12 parts, broad in the middle, but narrower near the poles of the zodiac; and each such part is called a sign and has a special name from the name of that sign which is intercepted between its two lines. And according to this acceptance, the stars which are near the poles are said to be in the signs.

Also, let a certain body be understood, the base of which is a sign, according to the sense in which we last accepted "sign," but the apex of which is upon the axis of the zodiac. Such a body, therefore, in a fourth signification is called a sign, according to which acceptance the whole world is divided into 12 equal parts which are called signs; and thus whatever is in the world is in some sign.

CONCERNING THE TWO COLURES:

There are, moreover, two other greater circles in the sphere which are called colures, whose duty is to distinguish the solstices and the equinoxes. A colure is said, however, from the Greek colon, which is a limb, and uros, which is a wild ox, because just as the tail of a wild ox, when raised, which is its limb, makes a semicircle and not a perfect circle, so the colure always appears to us imperfect, since only one half of it appears, while the other is hidden from us. The colure, therefore, distinguishing the solstices, passes through the poles of the world, through the poles of the zodiac, and through the maximum declinations of the sun, that is, through the first degrees of Cancer and Capricorn. Whence the first point of Cancer, where this colure intersects the zodiac, is called the point of the summer solstice, because when the sun is in it, it is the summer solstice, and the sun cannot approach closer to the zenith of our head. The zenith is, however, the point in the firmament placed directly above our heads. The arc of the colure, indeed, which is intercepted between the point of the summer solstice and the equinoctial, is called the maximum declination of the sun. And it is, according to Ptolemy, 23 degrees and 51 minutes. According to Almeon, however, 23 degrees and 33 minutes. Similarly, the first point of Capricorn, where the same colure intersects the zodiac from the other side, is called the point of the winter solstice, and the arc of the colure intercepted between that point and the equinoctial is called the other maximum declination of the sun, and it is equal to the former. The other colure, indeed, passes through the poles of the world and through the first points of Aries and Libra, where there are two equinoxes; whence it is called the colure distinguishing the equinoxes. These two colures intersect one another upon the poles of the world at right spherical angles. The signs of the solstices and equinoxes are evident from these verses: "These two solstices Cancer and Capricorn make, but Aries and Libra make the nights equal to the days."