What is in the picture?
A weather vane, wind 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, weather 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 weather vanes have pointers. When the wind is sufficiently strong, the head of the arrow or cockerel (or equivalent depending on the chosen design) will indicate the direction from which the wind is blowing.
The weather vane was independently invented in ancient China and Greece around the same time during the 2nd century BCE. The earliest written reference to a weather vane appears in the Huainanzi, and a weather vane was fitted on top of the Tower of the Winds in Athens.