OF THE WORLD. CHAPTER IX.

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A decorative woodcut initial 'I' featuring a human figure within an ornate floral and geometric border.
What a sign is.

I have said that the signs of the Zodiac are named after animals because of the effects the Sun produces upon entering each sign, and that they thus have a resemblance or property shared with the animal, or with the thing from which the sign takes its name. Because it seemed to me that I ought to declare this more fully, I will state in this chapter what a sign is, and in how many ways the term is used; also the resemblance that each sign has with the thing to which it is compared, and on what day of the year the Sun enters each sign, according to common opinion. First, it is to be noted that a "sign," according to Sacrobosco Johannes de Sacrobosco (c. 1195–1256) was the author of De sphaera mundi, the most influential astronomical manual of the Middle Ages and Renaissance., is a four-sided pyramid whose base or seat is the surface we call a "sign," and its point is toward the center [of the Earth]. There, these stars are marked, whose light or splendor the Astrologers In the 16th century, "Astrologer" and "Astronomer" were often used interchangeably, as the study of stars was used for both navigation and predicting the seasons. used to contemplate, by which they know what is to come, thereby foreseeing the qualities of Winter, Spring, Summer, and Autumn.
The principal stars commonly show the quality of the weather when they rise.

For the principal stars commonly show the quality of the weather when they rise. "Sign" can also be taken for that part of the zodiac which the Sun passes through after having completed thirty degrees of its movement. And because the Sun passes through the zodiac in one year—which consists of three hundred and sixty degrees—there are therefore twelve signs or "habitations" of the Sun. As Ptolemy Claudius Ptolemy (c. 100–170 AD), the Greco-Egyptian mathematician and astronomer whose geocentric model dominated European thought until the Copernican Revolution. says in the second book of the Quadripartite original: "Quadripartit"; this refers to Ptolemy's Tetrabiblos, a foundational text on the influence of celestial bodies., there are twelve signs corresponding to the twelve parts of the earth, of which the first is Aries The Ram.. The reason why this sign is named first among the others is, according to the opinion of some, that the Sun made its first movement in its first degree on the first day it was created, and created the equinox The vernal (spring) equinox.. Or, alternatively, it is because when the Sun enters this sign, it produces
Reason why the sign of Aries is named first among the others of the zodiac.

heat and humidity along with it, from which the vital movement of generation and growth is made. It is similarly said that this sign is called Aries for its comparison to the ram, which is weak in one part of its body and strong and firm in the other; just as when the Sun enters Aries on the eleventh of March These dates follow the Julian calendar, which was in use in 1569; they differ by several days from our modern Gregorian calendar., it warms little by little at the beginning, and then at the end one feels its greatest vehemence.
Taurus 2.

The second sign is called Taurus The Bull., to signify that just as the bull is a robust animal, so when the Sun enters this sign on the twelfth of April, it warms more strongly than before.
Gemini 3.

The third sign is Gemini The Twins., by which it is understood that when the Sun enters it on the eleventh of May, it engenders by its power, by heating—