How a Mill Worked
At first mills were constructed very simply. A structure that held a “water wheel” was built along a river or stream. The water wheel was placed partially into the water so that it could be turned by the force of the river. The center shaft of the wheel in a sawmill would power large saws that cut logs into boards.
Water powered mills were also used to grind grain into flour. They were called gristmills. The grain was crushed between rotating stones with surfaces designed with ridges and grooves. The space between the millstones had to be set carefully, close enough to grind all the grain but not to burn it or wear the surface. The millstones had to be sharpened often by the miller.
Later mills were built along a mill race. A mill race was a narrow canal where water was diverted from the river. Energy to turn the mill stones came from the waterwheel that was set in the millrace.
This illustration shows an example of one kind of mill. In this case water rushes over a large wooden waterwheel seen at the left of the diagram. A shaft connects the waterwheel to two large round flat stones. As the water wheel turns, the top millstone rotates. The bottom stone stays still. Kernels of grain are poured through a hole in the top stone and crushed between the heavy millstones as they rotate.