Concept

Weather vane

Summary
A wind vane, weather vane, or weathercock is an instrument used for showing the direction of the wind. It is typically used as an architectural ornament to the highest point of a building. The word vane comes from the Old English word fana, meaning "flag". Although partly functional, wind vanes are generally decorative, often featuring the traditional cockerel design with letters indicating the points of the compass. Other common motifs include ships, arrows, and horses. Not all wind vanes have pointers. In a sufficiently strong wind, the head of the arrow or cockerel (or equivalent) will indicate the direction from which the wind is blowing. Wind vanes are also found on small wind turbines to keep the wind turbine pointing into the wind. The oldest textual reference in China to a weather vane comes from the Huainanzi dating from around 139 BC, which mentions a thread or streamer that another commentator interprets as "wind-observing fan" (hou feng shin, 侯風扇). The Tower of the Winds on the ancient Greek agora in Athens once bore on its roof a weather vane in the form of a bronze Triton holding a rod in his outstretched hand, rotating as the wind changed direction. Below this was a frieze adorned with the eight Greek wind deities. The eight-metre-high structure also featured sundials, and a water clock inside. It dates from around 50 BC. Military documents from the Three Kingdoms period of China (220–280) refer to the weather vane as "five ounces" (wu liang, 五兩), named after the weight of its materials. By the third century, Chinese weather vanes were shaped like birds and took the name of "wind-indicating bird" (xiang feng wu, 相風烏). The Sanfu huangtu (三輔黃圖), a third-century book written by Miao Changyan about the palaces at Chang'an, describes a bird-shaped weather vane situated on a tower roof. The oldest surviving weather vane with the shape of a rooster is the Gallo di Ramperto, made in 820 and now preserved in the Museo di Santa Giulia in Brescia, Lombardy. Pope Leo IV had a cock placed on the Old St.
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