This diagram showing the structure of the cosmos comes from Nicephorus Blemmydes’ “Epitome physica.” At the center is the sphere of elemental earth surrounded by a narrow sphere of water. Then a broad sphere of air surrounds them capped by the sphere of fire. Separating the elements from the heaves is the sphere of the moon. Beyond that is the ether, the “ΑΙΘΗΡ,” where we see planets and stars. Beyond this is the “Water beyond the heavens” surrounded by the “Place of the angels.” A hierarchy of nine levels of angels, archangels, and beyond culminates in the Trinity at the top.
Born just before the Latins sacked Constantinople in 1204, Blemmydes fled the capital and studied mathematics, medicine, astronomy, logic, as well as theology and rhetoric in Asia Minor, especially Nicaea. He participated in the controversies between the Eastern and Western Churches, agreeing with the Western Church’s beliefs on such issues as the procession of the Holy Ghost from the Father through the Son. He was also renowned for establishing a school, where the young George Akropolites studied. Like so many Byzantine polymaths, he ultimately retired from public life to a monastery he had built.
This illustration from a 15th-century manuscript seems to be a type of geomantic figure that correlates the planets, signs, and figures (arrangements of dots). It shows the standard astrological relationships between planets and signs. Starting at the top and proceeding counterclockwise from the moon:
Moon — Cancer
Mercury — Gemini and Virgo
Venus — Taurus and Libra
Sun — Leo
Mars — Aries and Scorpio
Jupiter — Sagittarius and Pisces
Saturn — Capricorn and Acquarius
We also see a figure of dots associated with each planet/sign combination.
In its most generic sense, geomancy involved interpreting random markings of dots. Four rows of dots were grouped into figures, each named, associated with a planet, a sign, day or night, and other properties. There were sixteen such figures. This diagram was, perhaps, a form of geomancy or a related mantic practice (the generic title given to this work, “cleromancy”—divination by drawing lots, seems more closely related to the first figure than to this one.)
Various forms of divination were widely practiced (or at least discussed) throughout the Byzantine world, ranging from the recognizable astrology and necromancy to the relatively obscure (at least today) catoptromancy and lecanomancy—divination through interpreting images in mirrors or patterns in liquids in bowls. Both practices could both be part of long and complicated rituals that compelled demons to appear on the surface of the liquid or in the mirror. The demons could be commanded to reveal the future.
Apollodorus of Damascus is generally thought to have written the “Πολιορκητικά,” a treatise on siege engines, addressed to an unnamed emperor (probably Trajan). The text first treats siege engines used to besiege a hilltop fort, machines to protect troops from objects rolled down the hill as well as devices for protecting men attacking the base of the walls. It describes devices for drilling through walls and setting fire to walls as well as sheds for battering rams. The text also describes towers used to scale walls and invade a fort as well as towers with pivoting arms to sweep defenders off the walls.
Apollodorus worked on various engineering and building projects for the emperor Trajan in the early second century CE. He was responsible for such projects as Trajan’s Bridge over the Danube during the campaign in Dacia, Trajan’s Column and Trajan’s Forum, various triumphal arches, baths, and other smaller building projects. During Emperor Hadrian’s reign, he was banished and then executed around 130 CE.
Although Cosmas Indicopleustes is far from a household name, he enjoys an outsized reputation (at least in the abstract) as a representative of the benighted medieval belief that the earth was flat. To be sure, in his “Topographia Christiana” he says the earth is a parallelogram surrounded by oceans. Moreover, this parallelogram-shaped earth was stuffed inside a tabernacle-shaped cosmos. He thought the cosmos must be shaped like a tabernacle because its shape had inspired Moses to construct the Biblical tabernacle. Cosmas was not, however, a geographer nor was his “Topographia Christiana” clearly meant to represent physical reality. Moreover, there’s little evidence that anybody before the late 17th or early 18th century cared about Cosmas’s ideas. This didn’t stop people like Andrew White from making up stories about Cosmas having influenced medieval ideas about the construction of the earth. Alas.
In this 13th/14th-century copy of Cleomedes’ textbook on astronomy, typically referred to as “De motu circulari corporum caelestium,” is this illustration of Eratosthenes’ method for calculating the circumference of the earth. The outer oval is the signs of the zodiac in their zoomorphic/anthropomorphic forms, each labeled with its name. The sun is located in Cancer, in the upper right, illustrated by a head looking down and the label “ἥλιος.” Rays of light stream down on two cities. On the right is Syene; on the left is Alexandria (labeled accordingly). The city walls of each are adorned with a sundial. The gnomon on the dial in Syene is casts no shadow, since the sun shines down directly on the city. The gnomon in Alexandria would clearly cast a shadow, since the sunlight shines on the town at an angle. Between the two towns is a distance of 5,000 stadia, as noted by the “τὸ μεταξὺ στάδια Ε.” In the bottom is an illustration showing the path of the sun.
Cleomedes was a Greek astronomer active sometime in late antiquity (scholars don’t agree on when he lived). He is known primarily for his work, On the Circular Motions of the Celestial Bodies, a kind of textbook on astronomy. He preserves previous authors’ work, especially much of Posidonius’s work. He is also the earliest source for the story illustrated here about how Eratosthenes measured the circumference of the earth.