Cosmography Manuscript (12th Century)

Diagram of the Zodiac — “This wheel-shaped diagram shows the Earth at center, surrounded by the names of the months, the corresponding twelve signs of the zodiac, and an inscription explaining the relationships among the seven planetary bodies, the constellations of the zodiac, and the passage of time and its cyclical nature. Because it is the only illustration in this manuscript depicted on a blank page and the sole illustration that includes detailed, extensively colored figural imagery, the zodiacal diagram serves both as a frontispiece to the manuscript as a whole, and as an overview of the scientific and theological ideas presented in it.”

This wonderful series of medieval cosmographic diagrams and schemas are sourced from a late 12th-century manuscript created in England. Coming to only nine folios, the manuscript is essentially a scientific textbook for monks, bringing together cosmographical knowledge from a range of early Christian writers such as Bede and Isodere, who themselves based their ideas on such classical sources as Pliny the Elder, though adapting them for their new Christian context. As for the intriguing diagrams themselves, The Walters Art Museum, which holds the manuscript and offers up excellent commentary on its contents, provides the following description:

The twenty complex diagrams that accompany the texts in this pamphlet help illustrate [the ideas], and include visualizations of the heavens and earth, seasons, winds, tides, and the zodiac, as well as demonstrations of how these things relate to man. Most of the diagrams are rotae, or wheel-shaped schemata, favored throughout the Middle Ages for the presentation of scientific and cosmological ideas because they organized complex information in a clear, orderly fashion, making this material easier to apprehend, learn, and remember. Moreover, the circle, considered the most perfect shape and a symbol of God, was seen as conveying the cyclical nature of time and the Creation as well as the logic, order, and harmony of the created universe.

A couple of the diagrams feature the so-called “T-O map”, which Walters describes as “a conceptual diagram intended to show the relative positions of the three continents”.

The T, the Mediterranean Sea, separates Asia, Europe, and Africa, while the O is the surrounding ocean. Although the origins of the T-O map lie in the literature of classical antiquity, some of the earliest surviving pictorial examples occur in early medieval manuscripts of the works of Isidore of Seville.

Diagram of the Winds (I) — “The T-O map of the inhabited world occupies the center of this wheel-shaped diagram. Twelve profile busts of the winds, their Latin names provided in encircling bands, are depicted in the diagram’s wide outer ring; the narrower, unpainted ring just within it contains the winds’ Greek names. The four major winds are associated with the four cardinal directions, with East located at the top of the wheel. The busts of the winds blow toward the Earth at the center of the diagram, and their breath, represented as green strokes, flows into the wheel’s “spokes.” Each spoke bears a brief characterization of the associated wind, and these are expressed mainly in the first-person, as if spoken by the wind itself. Thus, the spokes of this diagram function like speech bubbles in a modern cartoon.”

Diagram of the Winds (II) — “Unlike the wind diagram on the preceding folio, this one is devoid of figural imagery or ornament. A schematic T-O map of the inhabited world occupies the center of the diagram. The wind names are written in the colored segments of the penultimate ring. Characterizations of each wind, comprising excerpts or adaptations of portions of the Spanish scholar Isidore of Seville’s (d. 636 CE) scientific work, De natura rerum (On the nature of things, XXXVII, i-iv), fill the corresponding trapezoidal sectors.”

Top: Diagram of the planetary orbits and zodiac; Bottom: Diagram of the planet cycles — “The wheel diagram at the top of the page shows the Earth at center, with the seven heavenly bodies–the Moon, Mercury, Venus, the Sun, Mars, Jupiter, and Saturn–orbiting in concentric rings. The zodiacal names are given in the diagram’s frame. As had the ancients, medieval authorities believed that the Earth lay at the center of the universe, and that the Sun, Moon, and planets circled it. Also following ancient writers, medieval authors called the planets “wandering stars” because of their eccentric orbits: the word “planet” derives from the Greek “planetoi,” for “wanderers.” Their orbits were calculated according to the length of time it took them to complete one circuit of the zodiac. In the wheel diagram in the bottom half of the page, the Earth at center is surrounded by concentric bands containing the names of the heavenly bodies and the intervals of their orbits.”

Diagram of the solstices and equinoxes — “This diagram shows the positions of the Sun on the days of the solstices and equinoxes. The center constitutes the observer’s position, facing south (the diagram’s top). The thin yellow band framing the diagram is the horizon. Six yellow circles connected by three red arcs of decreasing size indicate sunrise (left) and sunset (right) at the summer solstice, the spring and autumn equinoxes, and the winter solstice respectively, while the arcs themselves show the Sun’s path above the horizon on these days. At the arcs’ midpoints are the midday Suns of the solstices and equinoxes. Six straight red lines on either side of the midday Suns indicate the Sun’s positions at the third and ninth hours on these days.”

Diagram of the phases of the moon — “This diagram illustrates the Moon’s phases in relation to its distance from the Sun. The Earth at center is surrounded by three concentric rings. Along the inner ring are seven discs showing the phases of the waxing and waning moon, indicated by pale yellow wash emanating from the Sun, at right. As the diagram makes clear, and as medieval authorities recognized, the Moon’s phases are determined by the extent of its illumination by the Sun. The cycle begins with the new, crescent Moon at upper right (approximately 2 o’clock) and moves counterclockwise, with the days of the lunar cycle given in red. It ends when the Moon is not visible — that is, when it lies directly between the Earth and Sun, the latter labeled ‘Sol XXX.’ This day was called by Isidore of Seville (d. 636 CE) the “interlunar interval” (Etymologiae III, lv).”

Above: The harmony of the spheres; Below: The planetary orbits — “The idea of the harmony of spheres – that numerical proportions corresponding to musical harmonies governed both the movement of the seven heavenly bodies and their distance from the Earth – was taken up by medieval writers from ancient thought. In the illustration of the harmony of the spheres in the upper part of the page, the Sun, the Moon, and the five known planets are depicted as seven discs of equal size. Between them are written musical intervals — a tone (tonus), a semitone (semitonium), or three semitones (tria semitonia). The diagram below shows the Earth at center. The names of the zodiac are written in the outer frame. The names of the planetary bodies are written above their orbits, shown as red rings. Because each of these heavenly bodies has its own, eccentric orbit, the rings representing their orbits are not concentric.”

Diagram of planetary courses in the zodiacal signs — “In this diagram, the names of the seven planetary bodies – the Sun, the Moon, and the five known planets – are written along the vertical, at left. At top, along the horizontal, are the zodiacal names. One may follow the path of each planetary body through the zodiac by reading the graph from left to right. The diagram gives a sense not only of the independence of each planet’s orbit, but also of the different lengths of time it took each planet to complete one circuit of the zodiac. Along the bottom of the diagram is a list of the planetary bodies, with their distances given as musical values — a tone (tonus), a semitone (semitonium), or three semitones (tria semitonia) — as well as an abbreviated account of interplanetary distances, given as proportions of the distance from Earth to the Moon.”

Above: Diagram of the celestial climate zones; Below: Diagram of the terrestrial climate zones — “Following ancient writers, medieval scholars identified five climactic zones: the Arctic and Antarctic, or North and South frigid zones; the North and South temperate zones, extending from the Tropic of Cancer to the Arctic Circle and the Tropic of Capricorn to the Antarctic Circle; and the torrid zone between the two tropics. Only the temperate zones were thought to be habitable. In the upper diagram, the five climate zones are shown in an abstract configuration resembling a flower with five circular petals. In his De natura rerum, Isidore of Seville (d. 636 CE) relates the zones to the five fingers of the human hand. As the hand was a fundamental mnemonic tool in the ancient and medieval worlds, Isidore’s likening of the petals to fingers makes this diagram an effective memory device. In the lower diagram, the zones are rendered as if projected onto the globe, as arcs and circles.”

Above: Diagram of the terrestrial climate zones with the Riphaean mountains; Below: Diagram of the circuit of the moon in the zodiac — “In the diagram in the top half of the page, the observer’s point-of-view is the North Pole. This diagram is similar to the one in the lower part of fol. 6v, except that it also shows the Riphaean Mountains – a mythical range of peaks thought to mark the boundary between Asia and Europe, and the Arctic and North temperate zones — represented as seven abstract, colored silhouettes resembling triangular game-pieces. The diagram in the bottom half of the page charts the course of the Moon through the zodiac, correlating the lunar or synodic months and the zodiacal signs. According to the De natura rerum (On the nature of things) of the English scholar, Bede (d. 735 CE), the Moon journeys through the zodiac thirteen times in twelve lunar months; thus, it runs through each zodiacal sign in a little over two days and six hours.”

Above: Diagram of a cube; Below: Diagram of the microcosmic-macrocosmic harmony — “Two overlapping squares with a common diagonal create the cube in the upper diagram. The Sun is portrayed in the upper left corner, the Moon in the lower right. The four elements, Earth, Air, Fire, and Water, along with their respective properties, occupy the cube’s upper square. The wheel-shaped diagram in the bottom part of the page visualizes the idea that Man is a microcosm of the universe, and the universe a macrocosm of Man. Within the ring at center are the words (reading from top to bottom) “World,” “Man,” and “Year.” The eight intersecting arcs illustrate the relationships among the parts of the world – the four elements, the four bodily humors, and the four seasons. The cross shape created by the arcs expresses Christ’s role in restoring to nature its original harmony, order, and meaning, believed to have been disrupted by the Fall of Man.”