Weather vane

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. If employed on a boat, they are referred to as apparent wind indicators.

History

The oldest known textual references to weather vanes date from 1800-1600 BCE Babylon, where a fable called The Fable of the Willow describes people looking at a weather vane "for the direction of the wind." In China, the Huainanzi, dating from around 139 BC, mentions a thread or streamer that another commentator interprets as "wind-observing fan" (hou feng shin, 侯風扇).

The Tower of the Winds in the agora in Hellenistic 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 a frieze depicted the eight Greek wind deities. The eight-metre-high structure also featured sundials, and a water clock inside. It dated from around 50 BC.

Military documents from the Three Kingdoms period of China (220–280 AD) 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.

Vikings were known for creating ornamental, gilded weathervanes. They were originally crafted to adorn longships, however, became reappropriated for church use after the ships were retired. A notable example is the Söderala vane from c. 1050.

Christianity

Pope Gregory I (in office 590 to 604) regarded the cockerel as "the most suitable emblem of Christianity", being the emblem of Saint Peter (a reference to Luke 22:34 in which Jesus predicts that Peter will deny him three times before the rooster crows). Pope Leo IV (in office 847 to 855) had a weathercock placed on the Old St. Peter's Basilica or old Constantinian basilica. As a result of this, rooster representations gradually came into use as a weather vanes on church steeples, and in the ninth century Pope Nicholas I (in office 858 to 867) ordered the figure to be placed on every church steeple. The Bayeux Tapestry, likely commissioned by Bishop Odo of Bayeux in the 1070s, depicts a man installing a weathercock on Westminster Abbey.

One alternative theory about the origin of weathercocks on church steeples sees them as emblems of the vigilance of the clergy calling the people to prayer. Another theory says that the weathercock was not a Christian symbol but an emblem of the sun derived from the Goths.

A few churches used weather vanes in the shape of the emblems of their patron saints. The City of London has two surviving examples. The weather vane of St Peter upon Cornhill is not in the shape of a rooster, but of a key; while St Lawrence Jewry's weather vane has the form of a gridiron (symbolising Saint Lawrence).