It is called the Ecliptic because the eclipses of the sun and moon always occur under it.
The Signs are each the twelfth part of the Ecliptic or Zodiac, (30 degrees,) and are reckoned from the point of intersection of the ecliptic and equator at the vernal equinox.

They are named respectively Aries, Taurus, Gemini, Cancer, Leo, Virgo, Libra, Scorpio, Sagittarius, Capricornus, Aquarius, Pisces.

These names are borrowed from the constellations of the zodiac of the same denomination, which corresponded when these divisions were originally made; but in consequence of the precession, recession, or retrocession of the equinoxes, (about 50 1/10" yearly, at the rate of about 72 years to a degree, displacing an entire sign in about 2152 years, and making an entire revolution of the equinoctial in about 25,868 years), the positions of these constellations in the heavens no longer correspond with the divisions of the ecliptic of the same name, but are in advance of them.

Thus, the constellation Aries is now in that part of the ecliptic called Taurus, and the stars of Taurus are in Gemini, those of Gemini in Cancer, and so on throughout the ecliptic.
The relative positions of the signs and constellations in the zodiac and ecliptic seem thus to have gradually changed with the revolving years; and the worship of the three constellations, Taurus, Aries, and Pisces, with which Christianity is so intimately connected, seems to have changed in a corresponding degree.

The worship of the bull of Egypt--the celestial Taurus--has given place to that of the lamb of Palestine--the celestial Aries; and under the astronomical emblem Pisces--the twelfth sign of the zodiac--the dominant faith of to-day was appropriately taught by the twelve apostolic fishermen.
It is from one of these chosen fishermen, St.Peter, that the Pope of Rome claims to have derived his arbitrary power for binding and loosing on earth those who are to be bound and loosed in heaven.