Water mill at Acorn Bank

 The working water mill at the National Trust's Acorn Bank property near Penrith was having time out for work on the mechanism. There was an interesting display explaining the history of milling. It started with a pestle and mortar before developing into hand-driven stones before animals were used  and then mills. I was interested in the idea that the first water wheels were horizontal because they drove the shaft directly. I've been thinking about how you would deploy such a wheel. If it were in the stream, surely the stream would be pushing equally on both sides of the wheel and there would be no resultant torque. If only half the wheel were in the water, how would you stop water escaping?

 Vertical mill wheels turn a horizontal axle. For this to turn a vertical axle through the millstones, beveled gear wheels are needed. The mill wheel drives the gear wheel at the back in the picture above and a beveled wheel sits against it. I wonder how much energy is lost by transferring the drive between these two wheels. However much, it must have been more efficient to do it this way.