watermills can be divided into two kinds, one with a horizontal waterwheel on a vertical axle, and the other with a vertical wheel on a horizontal axle. the oldest of these were horizontal mills in which the force of the water, striking a simple paddle wheel set horizontally in line with the flow turned a runner stone balanced on the rynd which is atop a shaft leading directly up from the wheel. the bedstone does not turn. the problem with this type of mill arose from the lack of gearing; the speed of the water directly set the maximum speed of the runner stone which, in turn, set the rate of milling.