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How did Dutch windmills automatically turn to face the wind?

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Jacquard loom engraving, 1874 — automation At the top of the machine is a stack of punched cards that would be fed into the loom to control the weaving pattern. This method of automatically issuing machine instructions was employed by computers well into the 20th century.

To ensure windmills operate efficiently, their sails must face directly into the wind. Historically, this was achieved manually by using a long tailpole to rotate the entire mill body or its cap.12

The automation of this process was achieved through the invention of the fantail by Edmund Lee in 1745. The fantail consists of a set of five to eight smaller vanes mounted at a right angle to the main sails. These vanes are connected via gearing to wheels that run on a track around the mill’s cap or body.12

When the wind changes direction, it strikes the sides of the fantail vanes, causing them to rotate. This movement engages the gears and track wheels, which automatically turn the mill’s cap or body until the main sails are once again positioned squarely into the wind. This innovation significantly improved the efficiency and autonomy of wind-powered technology.12