The water wheel is connected to the millstones by gears. As a water wheel turns about 4 times a minute and the stones need to turn at 120 times a minute, two sets of gears are used to achieve this high speed. The wooden gears with removable teeth are true cogwheels.The cast iron gears are true gears. The iron gears speed up the motion 5 times and the wooden gears speed up the motion 6 times, giving an increase in speed of 30 times in all. The gears turn the stones from beneath by means a shaft which passes through the lower stone to engage with the runner stone above it.