Although now the fixed zodiac is an established fact, such an arrangement was undreamed of by the ancients, who regulated their almanacks from the actual sign at the time occupying the vernal equinoxial point; so that between the years 4340 B.C. and 2188 B.C. the sign of the bull was the first and chief sign of the zodiac, while during the two thousand years following—that is, until 36 B.C.—the sign of the ram or lamb took its place. The vernal equinox falls on March 21st each year, at which time the sun, having ascended from its lowest point of declination (December 21st), arrives at that portion of its annual course at which the equator and the ecliptic cross each other; and thus during the period when the sign of the bull was the vernal equinoxial sign the sun was said to be in _Taurus_, while in the following period, when the sign of the ram took the place of that of the bull, the sun was said to be in _Aries_. In order to understand thoroughly the apparent annual march of the sun round our earth, it will be necessary to observe the actual double motions of our earth round the sun and upon its own axis. Let us suppose that we are again in the period when the sun was in _Aries_ at the vernal equinox; on the 21st of March our earth, in travelling round the sun (annual motion), has reached a point at which the sun is placed between us and the first stars of _Aries_, which are then, of course, invisible, because when the sun is visible it is daytime—that is, the part of the earth on which we stand is opposed to the sun, which renders all the stars in that part of the heavens invisible; but, as the earth continues to turn upon its axis (daily motion), we gradually lose sight of the sun, and as the darkness closes around us the stars upon the opposite side of the heavens become visible; so that, when the sun is in _Aries_, or any other sign, that sign is always invisible to us, and at night we see the sign that occupies the opposite side of the zodiac. Day after day, as the earth continues to move round the sun, a few more stars in the sign _Aries_ are covered, until at the end of a month the sun reaches the next sign, _Taurus_; and the opposite signs, which we see at night, have also moved on to the same extent. Thus at noon on March 21st the sun is at its highest daily ascension, south of the zenith, or highest point of the heavens, obliterating by its effulgence the first stars of the sign _Aries_, through which it is apparently about to pass, and at midnight following the opposite sign, _Libra_, is seen at the same distance from the nadir, or highest point of the darkened heavens; while a month later, when the sun at noon is in _Taurus_, the sign _Scorpio_ is seen at the opposite point at midnight; and so on through all the signs, one month being occupied by the passing of the sun through each sign, so that it passes through _Aries_ in March, _Taurus_ in April, _Gemini_ in May, _Cancer_ in June, _Leo_ in July, _Virgo_ in