Weathervane

From Thomas Jefferson Encyclopedia

 Image of the weather vane
Image of the weather vane

The compass rose on the ceiling of the Northeast Portico was connected to the weathervane on the roof. Thomas Jefferson and his family could determine the wind direction without stepping outside by looking from the windows in the Entrance Hall and in the North and South Square Rooms.

Further Sources

Monticello Explorer: http://explorer.monticello.org/?s1=0|s4=12_10372