Fixten
that device how you discover it was also used with windmills, they just pull on an lever that puts the two gear together and the top stone spins while the grain is pooted into a hole in the top stone then flour comes from the sides where the two stones meet and is gathered in a trough that goes around the bottom stone to funnel to a chute that the bag is filled at. the vibration of the two stones grinding together moves the flourđ§