EARLY MAN-MADE CONTROL MECHANISMS

I was drawn towards the sight of a whitewashed stone windmill. It was high on the top of a conical hill in central Spain, its sails turning steadily in the breeze. The miller was pleased to show me around. The rotating sails, wooden gearing and turning millstones rumbled and creaked beneath the conical roof: a sound that cannot have changed for centuries. I knew that such windmills incorporated a primitive control mechanism to regulate the flow of corn, and I wanted to see it in operation. Suspended from the bottom of the hopper, a shallow sloping trough fed corn to a hole in the centre of the ‘running’ millstone. If the corn flows too fast the corn is incompletely ground; too slow and the flow of corn fails to keep the millstones apart, resulting in grit in the flour and millstones that soon need ‘dressing’. All this is prevented by a simple device which regulates the rate at which the corn flows. Attached to the hopper is a wooden ‘fiddle’ which rests on the rough-hewn surface of the ‘running’ millstone. As it turns, the fiddle dances over the surface, transmitting vibrations to the sloping trough.