Windswept_ The Story of Wind and Weather - Marq de Villiers [27]
Over the centuries, the wind rose was developed, first appearing on Portuguese and Spanish charts by the thirteenth century. Pliny notwithstanding, early wind roses denoted the direction of thirty-two winds, eight major winds, eight half winds, and sixteen quarter winds. Diagrammed into a circle, these thirty-two points resembled the European wild rose, with its thirty-two petals, hence the name. In after years, the symbol of the rose itself became a beacon for the lost, and when the compass was invented, the wind rose mutated into the equally ornate compass rose, which, often embellished with puffing wind gods, was still shown on maps in the nineteenth century and is still occasionally added by cartographers to give a satisfactorily antique tone to their products.
A typical wind rose. Sometimes these have fanciful illustrations of puffing wind gods, often not. Sometimes the four principal Greek winds are named; in most cases they are taken for granted.
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For the next few hundred years the two great branches of human endeavor—the practical, or artisanal, what we could today call the engineer; and the scholarly, or philosophical—went their separate ways, each developing its own brand of expertise. Practical men didn't bother with theory, the philosophers with experiment or observation. And so the theories of weather and wind that have survived tend to be the fruit either of pure reason innocent of observation or of visions; entirely missing are the thoughts of, say, a miller at his windmill, or a sea captain running before a gale, or a farmer who watched winds destroy or nurture his crops, or a roofer whose rafters collapsed in a storm. Typical of what did survive were the notions of eminent medieval scholar Hildegard of Bingen, a Benedictine sister at a nunnery in the Hunsruche near the Rhine. Sometime around 1145 she had a vision that the winds held all the elements together, each wind a wing of God working to keep the firmament in the right place, and causing it to rotate around the earth from east to west. Onto this lovely notion she then cobbled an impressively abstract view of how nature worked: The air was made of four layers, each governed by one of the cardinal winds. The east wind was closest to the ground; above it was the west wind, then the north, and finally the south. Within these layers everything else is to be found—the sun, the moon, all the constellations, storm clouds, and thunder. Hildegard was later beatified, but not for her work on the weather.
Throughout the medieval period, earlier theories persisted. Ger-vase of Tilbury wrote in Liber de mirabilibus mundi that "mountains and water cause winds." William of Conches maintained that four great ocean currents created the four cardinal winds. Sometime in the twelfth century Adelard of Bath produced his Quaestiones Naturalies, a compilation of seventy-six discussions of nature, including the weather. He ignored the Greeks, relying instead on imported Arab science, then the most mathematically inclined culture on earth. "Wind," Adelard asserted, "is merely a species of air."
Even by the time Columbus sailed the ocean blue the split between philosophy and science was still evident. The effects of winds, and their general direction, were known. The existence of the trade winds was known. Sails and sailing vessels were becoming ever more sophisticated devices for actually employing the winds. But the science of meteorology had scarcely improved, and natural philosophers, as they were coming to be called, were still enjoined in arcane debates about exhalations from the earth or the sea.
Nevertheless, the warning signs of bad weather were understood by those who needed to know them. Sullen swells in an eerie calm meant a storm was due. Red sky in