a 'chorus' of dancers, who "surround" heavy clouds and keep them in place. Aulus Gellius had already said something similar, but in reference to Caecias (a NE wind), not Corus. Others have related Corus to cover, conceal, because it relates to clouds, or perhaps the shower? Circius (NNW) – Isidore sees its circular or "bending" etymology and (perhaps a little confusingly) suggests its name is because it "bends into" Corus. Pliny and Aulus Gellius had already identified the Circius as the Mistral – Pliny calling it the violent wind of Narbonne, driving waves across to Ostia, while Aulus Gellius called it a local wind in Gaul, known for its dizzying, circular motion, and notes its alternate spelling Cercius in Hispania Isidore gives the Spanish name to be Gallicus, because it arises in Gaul. Vitruvius's 24-wind rose Chronologically, Vitruvius, who flourished in the late 1st century BCE, precedes all the Latin writers mentioned above: Seneca, Pliny, Aulus Gellius, etc. As such, his system of winds perhaps ought to be considered before the others. But Seneca quotes Varro as the source of his 12-wind system, and Varro wrote before Vitruvius. Moreover, Vitruvius's system is sufficiently distinct and peculiar to defy comparison with the others, and merits treatment in a special category all its own. Vitruvius, in his De architectura (c. 15 BCE), makes a rather approving mention of Eratosthenes's reduction of the winds from twelve to eight principal winds. But Vitruvius then goes on to note there are many other winds, only slightly different from the core eight, which have been given names of their own in the past. In a rather hurried fashion, Vitruvius relates an ample list of two variations on either side of the eight principal winds, which yield a wind rose of 24 winds. Although the 24 winds might be easier to draw equally spaced at 15° from each other, they are easier to list using modern half- and quarter-wind notation. No insinuation about degrees should be read into either case (principal winds are in bold): Many of the names in Vitruvius's list have appeared before elsewhere. Among the changes worth noting is the insertion of Gallicus (probably the Mistral) and Supernas (probably a local Alps lake breeze) in the very NE, nudging Aquilo (old NNE) to the NE (almost as in Pliny – perhaps the source of his confusion?). Old Boreas (now separate from Aquilo) is shunted