It will, of course, be seen that a thorough acquaintance with the foregoing matters is essential in order to acquire the faculty of distinguishing temperaments in every shape and variation: since it is sufficiently obvious that the effective influence of the stars must be greatly diversified by the constitutions of the seasons, as well as those of the ages of life, and of the angles; and also that the stars have a much stronger influence on any constitution, when there may not be in it any tendency contrary to their own, as the whole influence is then entire and unalloyed. For example, stars effecting heat operate more vigorously in constitutions of heat; and those effecting moisture in constitutions of moisture. On the other hand, should a tendency, contrary to their own, exist in any constitution, the stars accordingly become less efficacious; in consequence of being attempered and mixed with that contrary tendency: and this happens, for instance, when stars effecting heat are attempered by constitutions of cold, or stars producing moisture by constitutions of dryness. The influence of every star is thus modified by the proportionate admixture presented by constitutions of a nature different from its own. In succession to the previous instructions, the following description of the natural and peculiar properties of the signs of the zodiac is annexed: the general temperaments of the signs are analogous to those of the seasons, which are respectively established under each sign, but they have, also, certain peculiar energies, arising from their familiarity with the Sun, the Moon, and the stars, which shall be hereafter specified;—and the simple and unmixed influences existing in the signs, as considered only in themselves and with regard to each other, will be first stated. CHAPTER XIV TROPICAL, EQUINOCTIAL, FIXED, AND BICORPOREAL SIGNS Among the twelve signs, some are termed tropical, others equinoctial, others fixed, and others bicorporeal. The tropical signs are two: viz. the first thirty degrees after the summer solstice, which compose the sign of Cancer; and the first thirty degrees after the winter solstice, composing the sign of Capricorn. These are called _tropical_, because the Sun, after he has arrived at their first points, seems to _turn_, and to change his course towards a contrary latitude;[43] causing summer by the _turn_ he makes in Cancer, and winter by that which he makes in Capricorn. There are also two equinoctial signs: Aries, the first after the vernal equinox; and Libra, the first after the autumnal equinox: they are so called, because the Sun, when in the first point of either, makes the day and night equal.