8.11.2014

Sarah E. Bond: Mapping the Winds: Roman Anemoscopes and Meteorology

I thought I knew a great deal about the various instruments used by Romans in their daily lives. I have been rather fascinated for the past decade with what many would consider the mundane details (or "realia") of the ancient Mediterranean. So, imagine my surprise when I came across pictures of two wind-roses, called anemoscopes, which Romans used to gauge the wind.

The first is dated to the 2nd-3rd century CE and is now at the Vatican (IG XIV, 1308). It has both Latin and Greek labels for the winds. Liba Taub's book on Ancient Meteorology notes that it was found in Rome between the Esquiline and the Colosseum (2003: 107) [Compare with this one from the Italian city of Gaeta. IG XIV, 906]

Museo Vaticani, Vatican City. 
Another anemoscope has a similar dating (c.200 CE), and is now in Pesaro. It was discovered on the Via Appia outside the Porta Capena in Rome (Goodchild 2007: 134). It is not very large, just 21.6 inches in diameter and 2.7 inches thick. Like the Vatican anemoscope, it has a hole in the middle for a flag to be placed in it. The way the flag flaps can then be lined up on the disc in order to tell you the wind. On the Pesaro example, the twelve winds are delineated and then marked with small pegs. Most but not all anemoscopes had 12 winds, though this system was favored by people like Seneca. 

Pesaro Anemoscope. 

Wind roses could also be much larger than the Vatican or Pesaro examples. The most famous is the Tower of the Winds in Athens (2nd c. BCE [see Rehak]), which had a large weathervane on the top and was octagonal in shape. 

Tower of the Winds (or Horologion), Roman Agora, Athens.
The eight winds are depicted in relief on the sides.
Of lesser renown but similar use is the "Square of the Winds" at Dougga. It has a wind rose with 24 points celebrating the 12 winds. Like our smaller anemoscopes, it too is likely from the late second century, probably under Commodus. 

Pavement from the 'Square of the Winds', Dougga, North Africa.
A good question to ask is: why might Romans wish to use these contraptions? Sailors would of course desire to use them to aid navigation, but what about those on land? In his Natural History, Pliny gives us some insight, noting that strong winds could damage wheat and barley crops, particularly at various stages of the crop flowering. Moreover, certain crops benefited from particular winds. Cato apparently suggested olives should be planted due West. Pliny instructs individuals on how to create an anemoscope on their land by casting their shadow at midday. Likewise, Vitruvius earlier gave a more detailed description that matches up almost exactly with the layout of the Tower of the Winds. 

The winds were an important thing to diagram and to understand particularly for planning buildings. Pliny the Younger even oriented the cryptoporticus of his Laurentine villa so that the west wind, perceived as the healthy and life giving, could sweep through (Ep. 2.17.16-20). To Romans, the winds had different potencies than they do today. In book 18 of the Natural History, Pliny the Elder even suggested that Africus, the SW wind, could cause animals to become pregnant after coupling if they turned to face it. Finally, I would stress that there was a prevalent belief that certain winds brought certain patterns of weather. As the Venerable Bede lays out (On the Nature of Things, 27): Septentrio [N] brings cold and clouds, Circius [NNW] brings snow and hail. In a world without the weather channel, at least there was an anemoscope. 

Ornithon of Varro (1560-1590)
Photo via the British Museum.
Stephen McCluskey sums up the import of these anemoscopes generally in his remarks on medieval winds. He comments that into the Middle Ages, the directional winds supplied "architects with a guide for orienting homes and estates, scholars with a framework for geographical and cosmic orientation, and artists with ornamented motifs for mosaic and other decorative art" (1998: 15). At Casinum, Varro installed a weathervane on his elaborate aviary, which told visitors the direction of the winds outside and depicted stars on its ceiling inside--a mini cosmos depicting time and space. 

The legacy of mapping the winds continued into Late Antiquity and the Middle Ages. A manuscript of Isidore of Seville's work (d. 636) on winds from the 12th century, now at the Walters Art Museum in Baltimore, shows both the Latin and Greek names for the winds around a T-O map. It illustrates clearly that ordering the world also meant ordering the winds. 

Fol. 1v. Isidore of Seville, De Ventis. Rota map of the winds with T-O map.
(Photo from the Walters Art Museum Manuscripts).

References: 

Helen Goodchild, "Modelling Roman Agricultural Production in the Middle Tiber Valley, Central Italy" (PhD Thesis: U. Birmingham, 2007). 

Stephen McCluskey, Astronomies and Culture in Early Medieval Europe (Cambridge: Cambridge University Press, 1998). 

Barbara Obrist, "Wind Diagrams and Medieval Cosmology," Speculum 72.1 (1997), 40-41 [Fig.1-2], 48. 

Liba Taub, Ancient Meteorology (London: Routledge, 2003).  

Read Because It Is Cool:

Evelyn Edson and Emilie Savage-Smith, "An Astrologer's Map: A Relic of Late Antiquity," Imago Mundi 52 (2000), 7-29.  

Dave Potts, "Simulating Roman Trade Patterns" on the Archaeology of Portus site. 

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