Tetrabiblos and Centiloquy

Regarding the two primary materials original: "matieib⁹" (materiebus), referring to the four elements placed beneath the lunar circle, which are fire and air: these are surrounded and changed by the motion of the ether original: "alatbir" (al-athir), an Arabic-derived term for the celestial ether. These in turn surround the center, namely water and earth, and each of the plants original: "vegetabilia" within them. We believe there is no doubt that they are changed by their own transformations, because the sun and the air work upon all earthly things. Not only do alterations come to the earth during the four seasons of the year—such as in the conception of animals, the fruits of trees, the flooding of waters, and the changes of bodies—but also from the daily rotation in which it is daily contained. Indeed, because of this rotation, the earth grows hot and cold, dries out, and becomes moist in one and the same way, according to the consistent shapes the geometric aspects or alignments in appearance which are formed according to their positions from our zenith the point directly overhead.

From the moon likewise, because it is closer to the earth, a great force is attributed to us, by which changes are conferred upon many animate and inanimate things. For the flooding of rivers and their decrease happen according to the waning and waxing of the moon. The seas also are altered at its rising and setting. Likewise, plants and animals, in whole or in part, enter into growth or decay with its increase or decrease. The revolution of the wandering stars planets and the fixed stars produces heat, winds, and snow in the air surrounding us in many ways. Therefore, according to its temperament the "complexio" or mixture of qualities, alterations happen to the things placed beneath the earth. And according to their figures geometric relationships toward one another—which they receive from their conjunction and the mixing of their strengths—various changes of things occur. In these variations of things, which always proceed in an orderly fashion, the efficacy of the sun always prevails over the others.

The others, however, sometimes help it and sometimes hinder it; this happens more evidently and frequently in the moon, such as in conjunction, dichotomy the half-moon phase, and the full moon. In the other stars, however, it happens in a cycle of more time and with a more hidden significance, according to when they are in the hours of their occultation hiding behind another body and appearance, and their declination toward any latitude.

Therefore, since the work of the stars is thus disposed, it is necessary that what they perform by their motions appears not only in manifest things, but even in the beginning of the birth of seeds and fruits, so that their forms and modes are designated according to the qualities of the air in that very hour. Hence it is that farmers and keepers of livestock have experienced many things: in the hour of the mating of animals and the casting of seeds, they perceive what will come of it through the blowing of the winds. Generally, we also know that universal things, which are declared by the figures of the sun, moon, and stars, are plain and open. Indeed, the practitioners of this art recognize their prognostications of the sun through frequent experiments. Those effects of the stars which happen with the greatest forces, and which are accustomed to happen naturally, are prognosticated by the unlearned—and even by certain animals.

For we see that many animals signify the variations of the seasons of the year and the changes of the winds, which are called aulia likely a corruption or specific term for seasonal winds. We do not doubt that the occasion of these significations happens more frequently because of the sun. However, those things which happen with lesser forces are not prognosticated except by those with frequent experience, such as sailors who predict individual changes of wintry air and winds of longer duration. It is manifest that these happen through the figures of the moon and the fixed stars with the sun. But because many have been ignorant of the science of the locations of the stars and the hours of the aforementioned things, and the motions of the wandering stars planets which greatly assist the aforesaid, they have often been deceived in this science. Since this is so, if anyone has knowledge of the motions of all the stars and the sun and moon, so that he truly recognizes the places and hours in which their figures are formed, and does not forget their natures which he has learned through the experiments of many times—even if he does not know their substantial natures, but has recognized the effects they perform, such as the sun heating, the moon moistening, and similarly in the others—and if he were strong in this knowledge...